here are the logs:
[03:22:54] [main/INFO]: Loading Minecraft 1.20.1 with Fabric Loader 0.15.11
[03:22:54] [main/INFO]: Loading 46 mods:
- bitsandchisels 2.7.3
-- stacc 1.5.2+boneless2ahhhh
- fabric-api 0.92.2+1.20.1
|-- fabric-api-base 0.4.31+1802ada577
|-- fabric-api-lookup-api-v1 1.6.36+1802ada577
|-- fabric-biome-api-v1 13.0.13+1802ada577
|-- fabric-block-api-v1 1.0.11+1802ada577
|-- fabric-block-view-api-v2 1.0.1+1802ada577
|-- fabric-blockrenderlayer-v1 1.1.41+1802ada577
|-- fabric-client-tags-api-v1 1.1.2+1802ada577
|-- fabric-command-api-v1 1.2.34+f71b366f77
|-- fabric-command-api-v2 2.2.13+1802ada577
|-- fabric-commands-v0 0.2.51+df3654b377
|-- fabric-containers-v0 0.1.64+df3654b377
|-- fabric-content-registries-v0 4.0.11+1802ada577
|-- fabric-convention-tags-v1 1.5.5+1802ada577
|-- fabric-crash-report-info-v1 0.2.19+1802ada577
|-- fabric-data-attachment-api-v1 1.0.0+de0fd6d177
|-- fabric-data-generation-api-v1 12.3.4+1802ada577
|-- fabric-dimensions-v1 2.1.54+1802ada577
|-- fabric-entity-events-v1 1.6.0+1c78457f77
|-- fabric-events-interaction-v0 0.6.2+1802ada577
|-- fabric-events-lifecycle-v0 0.2.63+df3654b377
|-- fabric-game-rule-api-v1 1.0.40+1802ada577
|-- fabric-item-api-v1 2.1.28+1802ada577
|-- fabric-item-group-api-v1 4.0.12+1802ada577
|-- fabric-key-binding-api-v1 1.0.37+1802ada577
|-- fabric-keybindings-v0 0.2.35+df3654b377
|-- fabric-lifecycle-events-v1 2.2.22+1802ada577
|-- fabric-loot-api-v2 1.2.1+1802ada577
|-- fabric-loot-tables-v1 1.1.45+9e7660c677
|-- fabric-message-api-v1 5.1.9+1802ada577
|-- fabric-mining-level-api-v1 2.1.50+1802ada577
|-- fabric-model-loading-api-v1 1.0.3+1802ada577
|-- fabric-models-v0 0.4.2+9386d8a777
|-- fabric-networking-api-v1 1.3.11+1802ada577
|-- fabric-networking-v0 0.3.51+df3654b377
|-- fabric-object-builder-api-v1 11.1.3+1802ada577
|-- fabric-particles-v1 1.1.2+1802ada577
|-- fabric-recipe-api-v1 1.0.21+1802ada577
|-- fabric-registry-sync-v0 2.3.3+1802ada577
|-- fabric-renderer-api-v1 3.2.1+1802ada577
|-- fabric-renderer-indigo 1.5.2+85287f9f77
|-- fabric-renderer-registries-v1 3.2.46+df3654b377
|-- fabric-rendering-data-attachment-v1 0.3.37+92a0d36777
|-- fabric-rendering-fluids-v1 3.0.28+1802ada577
|-- fabric-rendering-v0 1.1.49+df3654b377
|-- fabric-rendering-v1 3.0.8+1802ada577
|-- fabric-resource-conditions-api-v1 2.3.8+1802ada577
|-- fabric-resource-loader-v0 0.11.10+1802ada577
|-- fabric-screen-api-v1 2.0.8+1802ada577
|-- fabric-screen-handler-api-v1 1.3.30+1802ada577
|-- fabric-sound-api-v1 1.0.13+1802ada577
|-- fabric-transfer-api-v1 3.3.5+8dd72ea377
-- fabric-transitive-access-wideners-v1 4.3.1+1802ada577
- fabricloader 0.15.11
-- mixinextras 0.3.5
- java 17
- minecraft 1.20.1
[03:22:54] [main/INFO]: SpongePowered MIXIN Subsystem Version=0.8.5 Source=file:/server/libraries/net/fabricmc/sponge-mixin/0.13.3+mixin.0.8.5/sponge-mixin-0.13.3+mixin.0.8.5.jar Service=Knot/Fabric Env=SERVER
[03:22:54] [main/INFO]: Compatibility level set to JAVA_16
[03:22:54] [main/INFO]: Compatibility level set to JAVA_17
[03:22:54] [main/INFO]: Initializing MixinExtras via com.llamalad7.mixinextras.service.MixinExtrasServiceImpl(version=0.3.5).
[03:22:57] [main/ERROR]: Minecraft has crashed!
net.fabricmc.loader.impl.FormattedException: java.lang.NoSuchFieldError: FORMAT
at net.fabricmc.loader.impl.FormattedException.ofLocalized(FormattedException.java:63) ~[fabric-loader-0.15.11.jar:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:472) ~[fabric-loader-0.15.11.jar:?]
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74) ~[fabric-loader-0.15.11.jar:?]
at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23) ~[fabric-loader-0.15.11.jar:?]
at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:69) ~[fabric-loader-0.15.11.jar:?]
Caused by: java.lang.NoSuchFieldError: FORMAT
at net.minecraft.class_1799.(class_1799.java:133) ~[server-intermediary.jar:?]
at net.minecraft.class_3727.(class_3727.java:16) ~[server-intermediary.jar:?]
at net.minecraft.class_3726.method_16194(class_3726.java:10) ~[server-intermediary.jar:?]
at net.minecraft.class_4970$class_4971.method_26218(class_4970.java:1028) ~[server-intermediary.jar:?]
at net.minecraft.class_2248.method_9579(class_2248.java:309) ~[server-intermediary.jar:?]
at net.minecraft.class_4970$class_4971$class_3752.(class_4970.java:1281) ~[server-intermediary.jar:?]
at net.minecraft.class_4970$class_4971.method_26200(class_4970.java:843) ~[server-intermediary.jar:?]
at net.minecraft.class_2246.(class_2246.java:1185) ~[server-intermediary.jar:?]
at net.minecraft.class_2358.method_10199(class_2358.java:326) ~[server-intermediary.jar:?]
at net.minecraft.class_2966.method_12851(class_2966.java:54) ~[server-intermediary.jar:?]
at net.minecraft.server.Main.main(Main.java:109) ~[server-intermediary.jar:?]
at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:470) ~[fabric-loader-0.15.11.jar:?]
... 3 more

the server is hosted on exaroton, and is on fabric 1.20.1 (0.15.11)

+1

+1

To fix this, install a newer version of Stacc. I used Stacc 1.7.0 in Fabric Loader 0.16.7 for Minecraft 1.20.1 and it worked for me. https://modrinth.com/mod/stacc-api