Server doesn't allow me to connect out of the blue.

So I'm hosting a modded server on version 1.16.5 with Forge 36.0.46, we've been playing for some time with no issue. Then, after a session of a few hours, we stop playing, but I decide to continue later that same day with a bit more building on our base, when suddenly, the server doesn't allow me to enter it. The errors have been "Timed Out", "Disconnected", or "An existing connection was forcibly closed by the remote host".

Additionally, on the server list there's this big red cross that reads "Incompatible FML modded server" and "Server network message list is not complete". As I understand, this is supposed to mean that the server and the client don't have the same versions or mods, but I know for a fact that isn't the case because just an hour before we played on the server no problem. I checked and all of the versions are up to date and are compatible on both server and client sides.

I have tried everything online, and removing the mods one by one hasn't allowed me to reach any solution as the server shows the same exact error messages. What strikes me is how out of the blue this was, it literally came from nowhere. Any advice on how to proceed?

It's on the latest version, same as Java.

Quote from AlexSV

Please share your server log and client log after trying to join.

I don't know where I can find the client log, but this is the server log: https://pastebin.com/YjAvU1FS

I found the client log: https://pastebin.com/vzZJ19RX

Hopefully its just the launcher, but is there some other launcher that I may use in order to test this? I haven't found any good alternatives, they all take ages to load, let alone play in a server.