Project Expiry

After a project expires (because of expired trial period), what is the way to activate it again? I have a licensed version now (I used a product key), and opened the projects using the licensed version, but the project keeps showing expired.

Am I supposed to use the calendar (publish settings) to change the date? Whatever I do, it is stuck at today's date and then shows expired the next day. Or am I just supposed to disable the Project Expiry check box. I see differing advice on the Internet.