Unable to Activate Presenter '13.

About three years ago I purchased Studio '13 and it has been working fine. Then a Windows 10 automatic update was installed and Articulate Presenter said I had to activate again. I tried to activate using the serial code I always had, but it didn't work. So several times I tried doing the manual activation using the code that was emailed to me and that did not work either. I read all the tips on the support website but that didn't help. I have two computers. It is working fine on the home computer but not the work computer. (It is my understanding that the license is good for two computers.) What can I do to activate my license?