Acrobat Pro 2017 (Classic) "Your trial has expired"

We're having some issues with licencing for Acrobat Pro 2017 (Classic) on our Remote Desktop Server (Windows Server 2012 R2)

It was installed in March and has been OK up until about a week ago, it's now giving a message stating the trial has expired. There were 5 licences purchased (Transactional Licencing Program) and the product was originally licenced and activated with the serial number provided for us in the Adobe LWS portal.

I've tried signing in and activating. I've uninstalled Acrobat, run the Acrobat clean up tool, rebooted the server and reinstalled. I've run then Acrobat Customization Wizard, added the serial number and enabled the Offline Exception. Users no longer are prompted to sign in but it's still stuck in a trial state. I've also tried to serialize it through the APTEE utility which seems to complete with a return code of 0 but still has the same issue.

Not really sure what to try next, hopefully someone here is able to assist.