In my case, I use Debian with the Virtualmin control panel installed. It has a useful tool to run Command shell using the browser window. So if you have access to your Virtualmin even if your IP is blocked for SSH or SFTP connecting, you're in luck.
Just go to your Virtualmin and click the Command shell button with the prompt icon. Probably on your left bottom, depending on the theme selected. Or use the Alt+K shortcut. Mac users will use Option+K.
Now the command line will appear. Provide this command and hit the Enter:
fail2ban-client set sshd unbanip 00.00.00.00
Of course, replace the 00.00.00.00 with your own IP address. The more generic command to unblock selected IP address from Fail2ban is:
fail2ban-client set JAILNAME unbanip IP_ADDRESS
As you can see, you just have to provide which jail you would like to unblock.