Cisco AAA/Identity/Nac :: 1120 - Registering ACS 5.2 Instance To Primary

When attempting to register an ACS instance to a primary (via System Administration -> Operations -> Local Operations -> Deployment Operations), I receive the following error as a popup in my browser:
 
"This System Failure occurred:  /opt/CSCOacs/db/acs.crt (No such file or directory). Your changes have not been saved.Click OK to return to the list page."
 
I had 2 ACS 1120 appliances clustered, 1 suffered a hardware failure about a year ago so I replaced it with a VM. That one is now the primary. I'm now wanting to replace the secondary instance (the remaining 1120 appliance) with a VM as well. I removed the current appliance from the network, installed the VM using the same IP address, and attempted to register. It failed as per the above error. After trying this a number of times, I then decided to return the 1120 appliance to secondary status and attempted to register it with the same results as above.