I renewed my update service for Xara Designer Pro X on 4/16/21 and today whenever I start the program a pop up appears trying to get me to renew my update service again and save 66%.
I think you can happily ignore the reminder notification but, to be certain, you could log into your Magix account go to My Products and check the details there of when your current Update Service for XDP is set to expire.
If there is a mistake on that My Products page and the update service expiration date is wrong, you need to contact infoservice@magix.net and ask them to correct this.
That suggestion to remove the Update Notifier also occurred to me but, having recently been "reminded" that the Update Service for one of my products was about to expire, having renewed it, the pop-up messages no longer appeared.