Nitro Pro 12: Digital IDs are broken. "The selected profile is missing its private key and cannot be used to sign this document"

[Eric Shreve]

Nitro Pro 12.12.1.522 no longer can use Digital IDs to sign documents.  I removed and recreated the digital IDs several times.  I uninstalled and reinstalled Nitro Pro 12 and it reverted to this down-rev version.  After reinstalling, it now says "The selected profile is missing its private key and cannot be used to sign this document" which is different than the original error message.  I've tried creating the Digital ID in both Windows Store and File formats to no avail.  I see this has happened several times before in the forum but the fix is never described.  How does one fix this?