Zimbra certbot LetsEncrypt - verification failure - expecting an RSA key

Zimbra Certbot LetsEncrypt I have installed a LetsEncrypt SSL certificate on a separate server for a different domain without problems. I followed the same procedures that I used on that server for a new server (Ubuntu Server - same as the other) and everything worked up until the verification.

** Verifying '/opt/zimbra/ssl/letsencrypt/cert.pem' against '/opt/zimbra/ssl/zimbra/commercial/commercial.key'

140072965674304:error:0607907F:digital envelope routines:EVP_PKEY_get0_RSA:expecting an rsa key:crypto/evp/p_lib.c:474:

ERROR: Certificate '/opt/zimbra/ssl/letsencrypt/cert.pem' and private key '/opt/zimbra/ssl/zimbra/commercial/commercial.key' do not match.

I have not been able to find any information on how to fix this problem.