Program not Activating

I recently just purchased a copy of Scrivener for Windows. The order was completed and everything went smoothly. I went to install the trial version so that I could activate my copy of the program. However, upon inserting my Serial Number Name and Serial Number, the program will prompt me with a “Successfully Registered” window, immediately followed by “This key is invalid,” or something of the sort, but it allows me to use the program completely. I have to do this process over and over again in order to use the program. What’s going on?