offlineActivationFileCreatedFailureAnswered

I have a customer whose license suddenly stopped working. The error is 28, and we're already troubleshooter that in the past without any resolution.

As a workaround, I asked him to generate an offline activation file and surprisingly, that is failing. I see ‘offlineActivationFileCreatedFailure’ but I don't have a way of troubleshooting the customer's system for details.

What could could have gone wrong here?