error message: activation key not valid

I have been using eMClient since 10-15-2017 without any problems.  Today on start-up I received a message that I needed to activate my software and a button to reactivate appeared.  I entered the password I was provided in 2017, but I now get “activation key is not valid” and will not allow me to use the software!  I’m running version 7.2.34062.0.  What should I do??

Activate it again?

That’s what I’m trying to do!  The pop-up box asks for the validation code and I put in the password I was given last year – and I get a message back that it is “not valid”.  It’s worked for a year – what’s changed?  There was an eMClient update a few days ago, plus Windows 10 updates monthly, but I still don’t understand why my password is now seen as “not valid”.  Do you have any suggestions?

Sorry I meant register it again. I don’t know if that’s possible