I am currently out of town, and my server went down. All my services go through nginx, and suddenly started giving error 502. My SSH won’t let me in. I had my sister reboot the server, and it still doesn’t work. I apologize for the lack of details, but that is all I know, and I can’t access logs. I’ve cleared cache, and used a VPN in case fail2ban got me. I recently got a tp link router, so it could be something with that, but it was working for a while. I will have her do another reboot, and if that doesn’t work I will have her power off and unplug the server in case it was hacked.
Edit: I have absolutely no clue why, but it works now. I literally did nothing. As far as I know, my sister hasn’t touched it today. It just started working. Computers, man…
Edit 2: Actually she said she did something. Not sure what, but it works now.
If it’s working again all of the sudden I would lean towards f2b. I don’t know what your “timeout” is, but if f2b got tripped it would explain why you couldn’t get in yesterday but today it works (assuming your ban expires in 24hrs or so).