Cannot activate fences, V.2 old account

I purchased Fences V.2 in 2015.  I had a disk crash two weeks ago, which I fixed, but since then, Fences keeps asking me to register.  When I register with the activation code, I get the messge:

Thank you! Fences has been successfully activated.

But after few hours, pop-up appears telling me to register.  I register again, and pop-up disappears for a few hours, and appears again.

I tried deleting some files as suggested in another thread, but it did not solve the problem.

Please let me know how I can fix this.