I've been working on this issue now for going on 8 hours. I've read every forum thread on the issue and I've tried everything I can try. My GoDaddy certificates have been installed and working fine for a year. So they expired a few days ago and I renewed but I can NOT get the new ones to install.

The most common error I get is Your certificate was not installed due to the error : system failure: XXXXX ERROR: Unmatching certificate (/opt/zimbra/mailboxd/webapps/zimbraAdmin/tmp/current.crt) and private key (/opt/zimbra/mailboxd/webapps/zimbraAdmin/tmp/current_comm.key) pair.

I tried manually moving the files over to the folder as suggested in this thread:
Zimbra 5.08 SSL Certificate Instalation But I'm still getting the above error.

I just upgraded to 5.16 hoping it would fix the issue but I'm still in the same boat.

I'm a NE customer so if I have to I'll file a bug fix for this.