How to stop pop up service notification at startup

I am using Parallels 15 on an iMac. Every time Parallels starts I get a pop up window telling me that a newer version of Parallels is available. I have checked the box in the window that says not to display this pop up again, but it doesn't work.
Can someone tell me if there is some way to stop these pop up messages without having to buy the latest version of Parallels?