Fix: Server Re-imaged? Run `ssh-keygen -R [IP]` to clear old key.
Fix: Server might be OFF. Firewall might be blocking Port 22. Check VNC.
Fix: Root login disabled? Use Key? Wrong password?
Fix: Run `htop`. Identify process. Kill if stuck.
Fix: MySQL crashing? Add Swap space. Upgrade RAM.
Fix: `du -sh /*`. Clear logs: `journalctl --vacuum-time=1d`.