While doing some trial and error tests, I used up all 5 issuance of the certificates and cannot reissue a new certificate. However I have saved a backup copy of one of the certificates (crt and key files). Now I can add that certificate via cpanel SSL/TLS Option but after adding it, the Let’s Encrypt app doesn’t recognize the certificates for auto renewal.
How can I add the previous (valid) certificates issued by Let’s Encrypt to the official Let’s Encrypt cPanel app so that it recognizes it and automatically reissue upon expiration?
I don't use cPanel, but I don't think this is possible. cPanel has it's own certificate management, you have to manipulate the configuration files directly. But without root access that may be impossible.
So wait 60 - 70 days, then create a new certificate via cPanel. Then the automation should work.