Can you think of what have you done to your server before that reboot?
Did you maybe enabled firewall or changed some SSH settings?
You can try going to Console from DigitalOcean Control Panel. From there, you can see does your Droplet even booted and if it is - you should check SSH configuration and restart SSH by running
- sudo systemctl restart sshd
While you’re there you can check does you enabled ufw firewall by running
If you want it disabled it should return something in lines
ufw is not running or
If it is enabled it will return
status: active and rules list. In that case makes sure on list is
22 for port and status is
If your Droplet is not booted try restarting again via Control Panel and post here so we can instruct you further :)
Addition: Make sure you can ping your Droplet from local PC. If ping is unsuccessful Droplet networking could be down, in that case Support can help you restore networking