Unable to reissue certificate for webmail when SSL/TLS support disabled: An error happened while reissuing the certificate: Validation failed

Symptoms

• 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:

  PLESK_ERROR: An error happened while reissuing the certificate: Validation failed

• SSL/TLS support option is disabled at Domains > example.com > Hosting&DNS > Hosting Settings.

Cause

Unclear

Resolution

1. Log into Plesk.
2. Unassign the current certificate from Domains > example.com > SSL/TLS Certificates > Unassign Certificate
3. 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.