This happened while I was loading up BOMD for the first time I tried different version and retried but every time it doesn't work I even switched computers!

This was the log:
java.lang.RuntimeException: Could not execute entrypoint stage 'main' due to errors, provided by 'bosses_of_mass_destruction'!
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:50)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke(EntrypointUtils.java:33)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointClient.start(EntrypointClient.java:33)
at net.minecraft.class_310.(class_310.java:437)
at net.minecraft.client.main.Main.main(Main.java:177)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:234)
at net.fabricmc.loader.launch.knot.Knot.launch(Knot.java:153)
at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28)
Caused by: java.lang.NoClassDefFoundError: software/bernie/geckolib3/GeckoLib
at net.barribob.boss.MainKt.init(MainKt.java:45)
at java.lang.invoke.MethodHandleProxies$1.invoke(MethodHandleProxies.java:187)
at com.sun.proxy.$Proxy22.onInitialize(Unknown Source)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointClient$$Lambda$2230/1756824688.accept(Unknown Source)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:47)
... 11 more
Caused by: java.lang.ClassNotFoundException: software.bernie.geckolib3.GeckoLib
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at net.fabricmc.loader.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:175)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 16 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Render thread
Stacktrace:
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:50)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke(EntrypointUtils.java:33)
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointClient.start(EntrypointClient.java:33)
at net.minecraft.class_310.(class_310.java:437)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.main.Main.main(Main.java:177)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:234)
at net.fabricmc.loader.launch.knot.Knot.launch(Knot.java:153)
at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28)

-- System Details --
Details:
Minecraft Version: 1.16.5
Minecraft Version ID: 1.16.5
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1685653992 bytes (1607 MB) / 3791650816 bytes (3616 MB) up to 4294967296 bytes (4096 MB)
CPUs: 6
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx4G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Fabric Mods:
adorn: Adorn 1.13.0+1.16.5
autoconfig1u: Auto Config v1 Updated 3.3.1
bosses_of_mass_destruction: Bosses of Mass Destruction (Beta) 1.2.3-1.16.5
byg: BYG 1.1.7
cardinal-components-base: Cardinal Components API (base) 2.8.1
cardinal-components-entity: Cardinal Components API (entities) 2.8.1
cloth-basic-math: Cloth Basic Math 0.5.1
cloth-config2: Cloth Config v4 4.11.14
extraorigins: Extra Origins 1.16.5-11
fabric: Fabric API 0.33.0+1.16
fabric-api-base: Fabric API Base 0.2.1+9354966b7d
fabric-api-lookup-api-v1: Fabric API Lookup API (v1) 1.0.0+dc716ea17d
fabric-biome-api-v1: Fabric Biome API (v1) 3.1.1+ca58154a7d
fabric-blockrenderlayer-v1: Fabric BlockRenderLayer Registration (v1) 1.1.5+ca58154a7d
fabric-command-api-v1: Fabric Command API (v1) 1.1.1+351679a77d
fabric-commands-v0: Fabric Commands (v0) 0.2.2+ca58154a7d
fabric-containers-v0: Fabric Containers (v0) 0.1.11+9354966b7d
fabric-content-registries-v0: Fabric Content Registries (v0) 0.2.1+ca58154a7d
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.1.3+ca58154a7d
fabric-dimensions-v1: fabric-dimensions-v1 2.0.6+9354966b7d
fabric-entity-events-v1: Fabric Entity Events (v1) 1.0.3+ca58154a7d
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.4.2+ca58154a7d
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.2.1+ca58154a7d
fabric-game-rule-api-v1: Fabric Game Rule API (v1) 1.0.6+ca58154a7d
fabric-item-api-v1: Fabric Item API (v1) 1.2.1+ca58154a7d
fabric-item-groups-v0: Fabric Item Groups (v0) 0.2.7+2868a2287d
fabric-key-binding-api-v1: Fabric Key Binding API (v1) 1.0.4+9354966b7d
fabric-keybindings-v0: Fabric Key Bindings (v0) 0.2.1+ca58154a7d
fabric-language-kotlin: Fabric Language Kotlin 1.6.5+kotlin.1.5.31
fabric-lifecycle-events-v1: Fabric Lifecycle Events (v1) 1.2.1+ca58154a7d
fabric-loot-tables-v1: Fabric Loot Tables (v1) 1.0.2+ca58154a7d
fabric-mining-levels-v0: Fabric Mining Levels (v0) 0.1.3+ca58154a7d
fabric-models-v0: Fabric Models (v0) 0.3.0+bc7a746f7d
fabric-networking-api-v1: Fabric Networking API (v1) 1.0.1+ca58154a7d
fabric-networking-blockentity-v0: Fabric Networking Block Entity (v0) 0.2.8+ca58154a7d
fabric-networking-v0: Fabric Networking (v0) 0.3.2+ca58154a7d
fabric-object-builder-api-v1: Fabric Object Builder API (v1) 1.9.4+9354966b7d
fabric-object-builders-v0: Fabric Object Builders (v0) 0.7.2+ca58154a7d
fabric-particles-v1: Fabric Particles (v1) 0.2.4+ca58154a7d
fabric-registry-sync-v0: Fabric Registry Sync (v0) 0.7.4+ca58154a7d
fabric-renderer-api-v1: Fabric Renderer API (v1) 0.4.2+2868a2287d
fabric-renderer-indigo: Fabric Renderer - Indigo 0.4.4+ca58154a7d
fabric-renderer-registries-v1: Fabric Renderer Registries (v1) 2.3.0+2868a2287d
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.1.5+ca58154a7d
fabric-rendering-fluids-v1: Fabric Rendering Fluids (v1) 0.1.13+ca58154a7d
fabric-rendering-v0: Fabric Rendering (v0) 1.1.2+ca58154a7d
fabric-rendering-v1: Fabric Rendering (v1) 1.6.0+2868a2287d
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.4.6+2868a2287d
fabric-screen-api-v1: Fabric Screen API (v1) 1.0.0+c045166c7d
fabric-screen-handler-api-v1: Fabric Screen Handler API (v1) 1.1.5+9354966b7d
fabric-structure-api-v1: Fabric Structure API (v1) 1.1.4+ca58154a7d
fabric-tag-extensions-v0: Fabric Tag Extensions (v0) 1.1.1+ca58154a7d
fabric-textures-v0: Fabric Textures (v0) 1.0.6+ca58154a7d
fabric-tool-attribute-api-v1: Fabric Tool Attribute API (v1) 1.2.6+ca58154a7d
fabricloader: Fabric Loader 0.11.7
fallflyinglib: FallFlyingLib 1.1.0
fatxporbs: Fat Experience Orbs 0.0.9
jankson: Jankson 3.0.1+j1.2.0
java: Java HotSpot(TM) 64-Bit Server VM 8
libcd: LibCapableData 3.0.3+1.16.3
libgui: LibGui 3.3.2+1.16.4
maelstrom_library: Maelstrom Library 1.2-1.16.5
minecraft: Minecraft 1.16.5
multipart_entities: MultipartEntities 1.1.1-SNAPSHOT
org_jetbrains_kotlin_kotlin-reflect: kotlin-reflect 1.5.31
org_jetbrains_kotlin_kotlin-stdlib: kotlin-stdlib 1.5.31
org_jetbrains_kotlin_kotlin-stdlib-jdk7: kotlin-stdlib-jdk7 1.5.31
org_jetbrains_kotlin_kotlin-stdlib-jdk8: kotlin-stdlib-jdk8 1.5.31
org_jetbrains_kotlinx_kotlinx-coroutines-core-jvm: kotlinx-coroutines-core-jvm 1.5.2
org_jetbrains_kotlinx_kotlinx-coroutines-jdk8: kotlinx-coroutines-jdk8 1.5.2
org_jetbrains_kotlinx_kotlinx-serialization-core-jvm: kotlinx-serialization-core-jvm 1.3.0
org_jetbrains_kotlinx_kotlinx-serialization-json-jvm: kotlinx-serialization-json-jvm 1.3.0
origins: Origins 0.7.3
origins-classes: Origins: Classes 1.1.1
pehkui: Pehkui 2.0.0+21w14a
reach-entity-attributes: Reach Entity Attributes 1.1.1
slimeorigin: Slimeorigin 3.0.0
tk_valoeghese_zoesteriaconfig: ZoesteriaConfig 1.3.2
Launched Version: fabric-loader-0.11.7-1.16.5
Backend library: LWJGL version 3.2.2 build 10
Backend API: NO CONTEXT
GL Caps:
Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fabric'
Type: Client (map_client.txt)
CPU:

You are missing some dependencies - geckolib (make sure it is fabric version). Also maybe cardinal components.