Took a server world into singleplayer, edited it & spit it back out onto the server, now nobody can join but me.

[Hukenon]

I downloaded the world (modded) from the server onto my computer and edited it with Amulet. By edit I mean I copied all the important builds, and pasted them onto a new world. I made sure to copy over all important files from the old world onto the new one (including playerdata). I excluded poi & region because Im pretty sure those are the actual "world". Anyways I sent this modified world back to the server, (deleting the old one and completely replacing it) and upon opening it everything seemed fine. Issue is, I (the owner) am the only person who can log in, everyone else is immediately met with a "session invalid" restart blah blah screen. I even deleted the playerdata folder after making a backup & tried but no, only I can join. I tried to join with someone else's account on my machine and that didn't work either. In the server console all it says is "User com.mojang.authlib.GameProfile@5caa82b5[id=<null>,name=The player's username,properties={},legacy=false] (/An IP im not sure if I should post it) has disconnected, reason: Disconnected"

I'm running a modded 1.16.5 server hosted by GGservers. The server's modpack is on technic, but I'm able to connect fine through the technic launcher. I'm not sure what to try next so any help is greatly appreciated.

[JaariAtmc]

Does this player have a mojang or microsoft account?

[Hukenon]

Yeah everyone does. All accounts have been migrated to Microsoft accounts aswell. I ended up turning off "online mode" in the server properties and using Local Looks mod to give everyone skins. And I renamed the player data files to the new UUIDs created when they joined to keep their stuff. It works fine so far but now if someone really wanted they could log in as anyone.