i installed TAN and Serene Seasons on a dedicated server, and it always crashes.
i tried:
changing the forge version,
changing the TAN's version,
nothing changed.
crash report: https://pastebin.com/5buGR0Y8

You're using an incredibly old version of Tough As Nails. You're going to have to update to Minecraft 1.12.2, as we don't support regular 1.12

i also tried the most new version and the same error occured. Sorry i didn't mention about it.

https://pastebin.com/WLj1PWZz
crashes even in the latest version of forge and TAN.

Have you tried just making a new world?

it crashes before it creates a new world file.

i dont know if this information would help or not, but i play in turkish language, and maybe 'ı' letter* is what's causing the problem

Oh, yeah, I see the weird "i" letter that it's trying to set the property as. I'm not really sure if there's anything we can do to fix that on our end though, as it seems to be something more at the operating system level.

well, it seems like me and my friend are going to play vanilla. its weird that it works on my client but crashes on server. anyways, thanks man.

it was because of my language. i researched a bit more and found out that this mod was fixing the turkish language problem: https://minecraft.curseforge.com/projects/localefixer
problem is fixed. i appreciate for your help.