SSH timing out + refusing keys
It all started when I ran a "reboot" command for the server while shelling in on PuTTY. SSH keys that were previously perfectly functional have stopped being accepted by the server. Have gone to control panel and verified private and public keys are matching, but server still refuses them.
The order of events changes seemingly at random. Sometimes it refuses what was once (and in theory should still be) a perfectly good key. Other times there is no attempt by the server to even authenticate with a key, instead asking for only user and pass (which, of course, fails). This occurs when both trying to login as a sudo-equipped user or as root.
That's if I get that far, which often I do not. Both PuTTY & WinSCP often end up with "Network error: Connection timed out" when attempting to shell into the droplet, even though the network ping for the IP from my computer is consistently around the 25ms mark.
Sometimes WinSCP will throw the error;
"Authentication failed. The server rejected SFTP connection, but it listens for FTP connections." However, this is at odds with http://www.infobyip.com/sshservertest.php, which confirms port 22 is open and listening, while plain FTP is being refused. I have also confirmed via the console access on DO that the ssh module is running, and have restarted it with no effect.
Everything was rosy and ticking over nicely until invoking "reboot" over SSH. So I imagine the cause has something to do with this. The server is now very slow and throwing semi-regular 502 errors too.
For reference, I am running LEMP with Ubuntu 14.04.