Hello and thanks to everyone who tried to help with an ACTUAL SUGGESTION.
Mainly to "Energen" with his:
It really was an USB issue, we repaired the device and plugged it back, rebooted and it worked, we are now in the process of transferring the configuration to another USB device that they will purchase a licence for as promised and hopefully - everything will work out fine for everyone.
To others who were more concerned that the client was using unlicenced software and that we should walk away from the job.
We are an IT SUPPORT company, not an IT WALK AWAY company.
If we have a client that asks for help, we do our best to HELP and straighten things up - and advocate for the "good guys" in the process.
For another client we managed to negotiate licencing a dozen computers with fake Autocad licences and went through hell and back to keep both sides happy in the process.
For everyone else who were more concerned about the licence issue and actually took time to write a help-less reply, figure this:
the modified version is OUT THERE, obviously, and people are using it. Eventually they might run in to the same problem as this client has - once you go with that version of the software there is no way from inside the system (if it's a PRO licence) to change the key, unregister it or something else and they are stuck with it - HINT, HINT, WINK, WINK developers!.
In my opinion, everyone who tried to help and gave a conctructive suggestion in this post did more for developers in the end than others who were more concerned about well being of our company and that of Unraid team.
There is a lesson for everyone here I guess.
Cheers!