While reissuing a new Let's Encrypt certificate for the webmail.example.com at Domains > example.com > SSL/TLS Certificates > Reissue Certificate the following error appears:
An error happened while reissuing the certificate: Validation failed
SSL/TLS support option is disabled at Domains > example.com > Hosting&DNS > Hosting Settings.
- Log into Plesk.
- Unassign the current certificate from Domains > example.com > SSL/TLS Certificates > Unassign Certificate
- Issue a new certificate for "
webmail.example.com" following this instructions.
Note: check if the certificate is showing properly using an incognito/private window to avoid browser's cache.