com.mojang.authlib.exceptions.AuthenticationException: Unable to extract valid-cased username!
at com.mojang.authlib.yggdrasil.YggdrasilAuthenticationService.makeRequest(YggdrasilAuthenticationService.java:79) ~[YggdrasilAuthenticationService.class:?]
at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService.fillGameProfile(YggdrasilMinecraftSessionService.java:180) [YggdrasilMinecraftSessionService.class:?]
at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService$1.load(YggdrasilMinecraftSessionService.java:60) [YggdrasilMinecraftSessionService$1.class:?]
at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService$1.load(YggdrasilMinecraftSessionService.java:57) [YggdrasilMinecraftSessionService$1.class:?]
at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3716) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2424) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2298) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2211) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache.get(LocalCache.java:4154) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:4158) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:5147) [minecraft_server.1.12.2.jar:?]
at com.google.common.cache.LocalCache$LocalLoadingCache.getUnchecked(LocalCache.java:5153) [minecraft_server.1.12.2.jar:?]
at com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService.fillProfileProperties(YggdrasilMinecraftSessionService.java:170) [YggdrasilMinecraftSessionService.class:?]
at moe.plushie.armourers_workshop.common.GameProfileCache$ProfileDownloadThread.fillProfileProperties(GameProfileCache.java:182) [GameProfileCache$ProfileDownloadThread.class:?]
at moe.plushie.armourers_workshop.common.GameProfileCache$ProfileDownloadThread.run(GameProfileCache.java:149) [GameProfileCache$ProfileDownloadThread.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_242]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_242]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_242]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_242]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_242]

Sorry, 1.7/1.12 is no longer supported

What launcher
What bundle?
What version of the game?
The full startup log would help.

A bundle, when from the client and server, the players' sessions are taken from their site
1.12.2
There are no startup errors. The only error is when you click on any thing in the global library
As well as a bug with textures when you open the container inventory