If I enter the CORRECT activation text, the program will be activated. If I then quit the program and then restart it, I have to enter it again. It's annoying because it repeats itself over and over again.
Sounds like an issue with writing the data to disk. Are you on Windows or Mac? Does other settings seem to get saved, such as window size, recent documents etc?
You can try Help > Open storage folder to see the data saved by the application. One level up there should be a folder named ELS where the license activation info is stored.