cPanel fails to secure cPanel/WHM login with proper certificate

At the moment there is an ongoing issue with either cPanel's or their SSL provider Sectigo services to issue certificates. They are regularly overloaded. If you are finding you do not have a valid certificate for your hostname (and it definitely resolves to the correct IP - main server IP), then you can request a new certificate in WHM -> Terminal with the command:

/usr/local/cpanel/bin/checkallsslcerts

If you get an error:

The cPanel Store returned an error (X::TemporarilyUnavailable) in response to the request “POST ssl/certificate/whm-license/90-day”: We were unable to process your request. Please try again later.

This means that the server is overloaded, simply retry the command - keep retrying until it comes up with:

Requesting certificate from cPStore …
Order submitted. (Order item ID: 2059747721)

Once you get that message then you are in business and the new SSL will be available within 5 minutes for your cPanel and WHM logins when you use the hostname e.g. https://vps.yourdomain.com:2083 or https://vps.yourdomain.com:2087