Yesterday, sftp was working fine, and today I can't establish a connexion to my server through sftp.

It's surprising because I didn't change anything and I didn't update any package.

I am using sftp (ftp through ssh) on port 22, and now I have the error message on my client (Fireftp of Firefox) which is
Can't establish a connexion. Please try again later.

I don't know which log file to check, there is nothing on /var/log/auth.log.

It's like the port 22 is blocked and yet I didn't modified anything.

Thank you for your help.