The page SSL/TLS Certificates at Domains > example.com fails to open:
A table must have a primary key, but none was found for table 'Orders'
Let's Encrypt certificate of a domain is not renewed automatically.
Corrupted database of the SSL It! extension.
Reinstall the extension:
Uninstall the SSL It! extension (on Windows Server, start a command prompt as an Administrator):
# plesk bin extension --uninstall sslit
Install the extension back:
# plesk bin extension --install sslit