We have a small minecraft server with 4 of my friends
A few days ago, a similar error occurred to 2 of my friends but suddenly disappeared after a day or two (they both said that after a few tries of connecting to the server, they both gave up and didnt try again until the next day. they said they didnt change or do anything)
2 days ago, this started happening to me and every time I join our server, I get disconnected after a few seconds. This happens 9/10 times.
I have tried using a VPN, disabling firewall, the ipconfig stuff, deleting and reinstalling minecraft, used a different internet connection (tethered on my phone, signal was bad and it was extremely laggy but i was still able to do stuff ingame and wasnt disconnected.), and that one advice regarding hamachi (I've never used that app before but I still used that advice just in case)
On the server list, I am able to see and ping our server fine. My internet connection is fine (I'm able to play other online games with good pings)