In "My Products" it shows Music Maker and date of purchase (Nov 2020) but it doesn't show a serial number. The product wants a serial number that starts with P3. How can I find it?
Welcome to the Magix user to user forums.
Exactly which variant of MM do you have, Basic (Free), Plus or Premium? You say you bought the app but the absence of a serial number suggests you actually have the Free version since Plus and Premium are "paid-for" variants.
Did you check carefully the email you would have received when making the purchase? Any needed serial number should have been included there.
If not, and you did "buy" it, try using this page to raise a ticket with Sales.
HTH
Jeff
Forum Moderator