Good afternoon!
I have encountered a very rare bug in minecraft. I play minecraft with mods on version 1.20.1 (forge-1.20.1-47.2.0-installer). At first everything was as usual, I created a server, put there mods, start the server, go there, check the mods and exit. I did this process very many times to make sure it was working correctly. But at one point the server stopped starting, it began to give the following error (I will describe briefly):  

[Yggdrasil Key Fetcher/ERROR] [com.mojang.authlib.yggdrasil.YggdrasilServicesKeyInfo/]: Failed to request yggdrasil public key
com.mojang.authlib.exceptions.AuthenticationUnavailableException: Cannot contact authentication server
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Caused by: java.net.SocketTimeoutException: Connect timed out

In the game itself, I can not go to any server, although before I was perfectly able to go to any server, also I can not change my skin in the game. In my account on the site Minecraft.net, I see that my skin has changed, but in the game it remains unchanged. Now I want to add the most important thing that this problem occurs only on Minecraft forge! On Minecraft fabric, Minecraft vanilla, Minecraft quilt such a problem is not, everything works stably, I can change skins and connect to servers!!!! In my opinion, it looks like the system blacklisted my ip because I was logged in and out of the server very often. This is the first time I've run into this problem in my several years of playing minecraft. 
There is nothing wrong with my internet connection as vanilla minecraft is working correctly
My system is fine too, I installed a new windows.

server log - https://paste.ee/p/jVMxE

Backup and delete the server.properties file and restart the server

Hey there,

It sounds like you're encountering a pretty specific issue with Minecraft Forge, particularly with the Yggdrasil authentication server. This can be a bit of a headache, but there are a few things you could try to fix this. First, it's worth checking your firewall and antivirus settings. Sometimes, these can interfere with your connection to Minecraft's servers. You might want to ensure that both Minecraft and Forge are on the allowed list.

Another thing you could try is resetting your internet connection. Even though everything else seems to be working fine, a simple reboot of your router might do the trick. It's one of those 'turn it off and on again' solutions, but surprisingly, it often works.

Lastly, it could be an issue with your Forge installation. Maybe there's a corrupted file causing problems. Reinstalling Forge for version 1.20.1 might help iron out any kinks. It's a bit of a process, but it's worth a shot.

I hope one of these solutions helps you out. It's frustrating when you run into these kinds of issues, but with a bit of troubleshooting, you should be able to get back to your game.

Good luck!