Apologies that no-one has responded to your question, perhaps because none of us has ever seen this problem before!
My only suggestion is to log out of the store and then log back in. To do this click on your email address showing at the top right corner (I would strongly recommend hiding it in your image or you may well be deluged with spam) and you will see this screen:
(Notice I have blanked my email address!).
Just ensure you have your serial number to hand - if you don't have it go to your Magix Account page, log in and find it under "My Products" - and press the highlighted "Log out" button.
I think if you then restart MM you may be still in the same loop so, initially at least, don't close and restart the app but rather choose the option, under Help to "log into store".
Did this work? Can you now see the Soundpools/Store content? Please let us know.