Hi I'm having this very same issue with music maker 2023 edition premium I downloaded and updated it from the email I was sent now I can't log in to the software at all I'm using windows 11 amd ryzen 7 CPU GeForce rtx 3070ti and I've never had this issue after upgrading before also the day after I was charged £49.99 you changed the price to £24.99 which I find very disrespectful you prompt me through emails and popups to constantly update I do and then you lower the price in a way I feel ripped off and like I've been given a dodgy download from my services I even tried to redownload it there it installed but still proceeds to not let me log into the store the login/register button does absolutely nothing I've removed the whole program and reinstalled it from my disc and then tried upgrading the whole reason I didn't get the disc with the new version this time was that I hadn't got the money but then I find out after installing the new version you've dropped the price by 70%
Just to add one thing to what @SP. has advised, and for your information: these are user to user forums, so not a contact for any Magix staff and we have nothing whatsoever to do with any pricing changes, sorry.
However, I do understand your annoyance at the "overnight" price change. It is quite possible for you to request a refund of your "higher-priced" purchase and then re-purchase the software at the lower price. To request the refund send full details of your original order to firstname.lastname@example.org and ask they they action the refund for you.