Some sites’ SSL certificates are not automatically renewing when using Cyberpanel. For the solution:
acme.sh --register-account -m my@example.com
You can replace my@example.com with your own email, or you can execute the command via SSH directly as shown above. Providing the email in the command resolves the issue.
Afterwards, if you re-issue the SSL specifically for the site in Cyberpanel, you will see that the problem is resolved.