So every time I load the game it stops and tells me there's an error during the start-up phase, I tried 3 different forge versions and 3 different versions of the mod.
Here's the crashlog.
---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 3/28/21 2:00 AM
Description: Mod loading error has occurred

java.lang.Exception: Mod Loading has failed
at net.minecraftforge.fml.CrashReportExtender.dumpModLoadingCrashReport(CrashReportExtender.java:85) [?:?] {re:classloading}
at net.minecraftforge.fml.client.ClientModLoader.completeModLoading(ClientModLoader.java:188) [?:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.lambda$null$1(Minecraft.java:508) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft$$Lambda$4243/1376201797.run(Unknown Source) [?:?] {}
at net.minecraft.util.Util.func_215077_a(Util.java:320) [?:?] {re:classloading}
at net.minecraft.client.Minecraft.lambda$new$2(Minecraft.java:504) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft$$Lambda$3969/1131724881.accept(Unknown Source) [?:?] {}
at net.minecraft.client.gui.ResourceLoadProgressGui.func_230430_a_(ResourceLoadProgressGui.java:113) [?:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.GameRenderer.func_195458_a(GameRenderer.java:481) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_195542_b(Minecraft.java:976) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:607) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(Main.java:184) [?:?] {re:classloading,pl:runtimedistcleaner:A}
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_51] {}
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_51] {}
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_51] {}
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_51] {}
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:51) [forge-1.16.5-36.1.2.jar:36.1] {}
at net.minecraftforge.fml.loading.FMLClientLaunchProvider$$Lambda$445/1884387196.call(Unknown Source) [forge-1.16.5-36.1.2.jar:36.1] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.0.9.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.0.9.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.0.9.jar:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.0.9.jar:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.0.9.jar:?] {}

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

-- Head --
Thread: Render thread
Stacktrace:
at corgiaoc.byg.config.json.subbiomedata.SubBiomeDataListHolderSerializer.deserialize(SubBiomeDataListHolderSerializer.java:85) ~[?:1.1.14] {re:classloading}
-- MOD byg --
Details:
Mod File: byg-1.1.14 (1).jar
Failure message: Oh The Biomes You'll Go (byg) encountered an error during the common_setup event phase
java.lang.NullPointerException: null
Mod Version: 1.1.14
Mod Issue URL: https://github.com/CorgiTaco/BYG/issues
Exception message: java.lang.NullPointerException
Stacktrace:
at corgiaoc.byg.config.json.subbiomedata.SubBiomeDataListHolderSerializer.deserialize(SubBiomeDataListHolderSerializer.java:85) ~[?:1.1.14] {re:classloading}
at corgiaoc.byg.config.json.subbiomedata.SubBiomeDataListHolderSerializer.deserialize(SubBiomeDataListHolderSerializer.java:13) ~[?:1.1.14] {re:classloading}
at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:69) ~[gson-2.8.0.jar:?] {}
at com.google.gson.Gson.fromJson(Gson.java:887) ~[gson-2.8.0.jar:?] {}
at com.google.gson.Gson.fromJson(Gson.java:825) ~[gson-2.8.0.jar:?] {}
at corgiaoc.byg.config.json.BYGJsonConfigHandler.handleBYGSubBiomesJSONConfig(BYGJsonConfigHandler.java:222) ~[?:1.1.14] {re:classloading}
at corgiaoc.byg.config.json.BYGJsonConfigHandler.handleOverWorldConfig(BYGJsonConfigHandler.java:65) ~[?:1.1.14] {re:classloading}
at corgiaoc.byg.BYG.commonSetup(BYG.java:80) ~[?:1.1.14] {re:classloading}
at corgiaoc.byg.BYG$$Lambda$3157/1934226640.accept(Unknown Source) ~[?:?] {}
at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:247) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:239) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus$$Lambda$2944/1979825302.invoke(Unknown Source) ~[?:?] {}
at net.minecraftforge.eventbus.EventBus$$Lambda$2580/1060327212.invoke(Unknown Source) ~[?:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.fml.javafmlmod.FMLModContainer.acceptEvent(FMLModContainer.java:120) ~[?:36.1] {re:classloading}
at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:121) ~[?:?] {re:classloading}
at net.minecraftforge.fml.ModContainer$$Lambda$3117/1487059223.run(Unknown Source) ~[?:?] {}
at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1618) ~[?:1.8.0_51] {}
at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1610) ~[?:1.8.0_51] {}
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289) ~[?:1.8.0_51] {}
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056) ~[?:1.8.0_51] {}
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1689) ~[?:1.8.0_51] {}
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157) ~[?:1.8.0_51] {}

-- 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: 625297928 bytes (596 MB) / 2147483648 bytes (2048 MB) up to 2147483648 bytes (2048 MB)
CPUs: 16
JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
ModLauncher: 8.0.9+86+master.3cf110c
ModLauncher launch target: fmlclient
ModLauncher naming: srg
ModLauncher services:
/mixin-0.8.2.jar mixin PLUGINSERVICE
/eventbus-4.0.0.jar eventbus PLUGINSERVICE
/forge-1.16.5-36.1.2.jar object_holder_definalize PLUGINSERVICE
/forge-1.16.5-36.1.2.jar runtime_enum_extender PLUGINSERVICE
/accesstransformers-3.0.1.jar accesstransformer PLUGINSERVICE
/forge-1.16.5-36.1.2.jar capability_inject_definalize PLUGINSERVICE
/forge-1.16.5-36.1.2.jar runtimedistcleaner PLUGINSERVICE
/mixin-0.8.2.jar mixin TRANSFORMATIONSERVICE
/forge-1.16.5-36.1.2.jar fml TRANSFORMATIONSERVICE
FML: 36.1
Forge: net.minecraftforge:36.1.2
FML Language Providers:
[email protected]
minecraft@1
Mod List:
forge-1.16.5-36.1.2-client.jar |Minecraft |minecraft |1.16.5 |SIDED_SETU|NOSIGNATURE
byg-1.1.14 (1).jar |Oh The Biomes You'll Go |byg |1.1.14 |ERROR |NOSIGNATURE
forge-1.16.5-36.1.2-universal.jar |Forge |forge |36.1.2 |SIDED_SETU|22:af:21:d8:19:82:7f:93:94:fe:2b:ac:b7:e4:41:57:68:39:87:b1:a7:5c:c6:44:f9:25:74:21:14:f5:0d:90
BiomesOPlenty-1.16.4-13.0.0.431-universal.jar |Biomes O' Plenty |biomesoplenty |1.16.4-13.0.0.431 |SIDED_SETU|NOSIGNATURE
Crash Report UUID: 9a04f58f-e482-47f5-9352-8c0eae438f0c

Reset your configs by deleting the byg folder in your config folder