[18Jan2021 11:46:03.581] [main/WARN] [net.minecraft.server.Main/]: Failed to load datapacks, can't proceed with server load. You can either fix your datapacks or reset to vanilla with --safeMode
java.util.concurrent.ExecutionException: java.lang.IllegalStateException: Missing required tags: minecraft:fluid:forge:milk
at java.util.concurrent.CompletableFuture.reportGet(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture.get(Unknown Source) ~[?:1.8.0_261]
at net.minecraft.server.Main.main(Main.java:130) ~[?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_261]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_261]
at net.minecraftforge.fml.loading.FMLServerLaunchProvider.lambda$launchService$0(FMLServerLaunchProvider.java:51) ~[forge-1.16.5-36.0.1.jar:36.0]
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.0.9.jar:?]
at net.minecraftforge.server.ServerMain$Runner.runLauncher(ServerMain.java:63) [forge-1.16.5-36.0.1.jar:?]
at net.minecraftforge.server.ServerMain$Runner.access$100(ServerMain.java:60) [forge-1.16.5-36.0.1.jar:?]
at net.minecraftforge.server.ServerMain.main(ServerMain.java:57) [forge-1.16.5-36.0.1.jar:?]
Caused by: java.lang.IllegalStateException: Missing required tags: minecraft:fluid:forge:milk
at net.minecraft.tags.NetworkTagManager.lambda$reload$1(NetworkTagManager.java:47) ~[?:?]
at java.util.concurrent.CompletableFuture.uniAccept(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$UniAccept.tryFire(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$Completion.run(Unknown Source) ~[?:1.8.0_261]
at net.minecraft.resources.AsyncReloader.func_219557_a(SourceFile:71) ~[?:?]
at net.minecraft.resources.AsyncReloader.func_219560_a(SourceFile:70) ~[?:?]
at java.util.concurrent.CompletableFuture$UniCompletion.claim(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture.uniAccept(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$UniAccept.tryFire(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture.postComplete(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture.complete(Unknown Source) ~[?:1.8.0_261]
at net.minecraft.resources.AsyncReloader$1.func_216873_a(SourceFile:53) ~[?:?]
at net.minecraft.resources.AsyncReloader$1.func_216872_a(SourceFile:50) ~[?:?]
at java.util.concurrent.CompletableFuture.uniCompose(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$UniCompose.tryFire(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture.postComplete(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$AsyncSupply.run(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.CompletableFuture$AsyncSupply.exec(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.ForkJoinTask.doExec(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source) ~[?:1.8.0_261]
at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source) ~[?:1.8.0_261]

Not 100% if this is you, or forge, given the change notes for 36.0.1, but posting here first.

IF Version is industrial-foregoing-1.16.4-3.2.8.3-7ac4a96

I think this is caused by MinecraftForge/MinecraftForge#7294 changing the tag type to whatever that optional stuff is, unsure.

Nvm, this is caused by Buuz removing milk from his registration, but not removing the tag definitions

Fixed in #968