unable to use the coupon that was emailed on registration of Movie edit pro plus 2020 (windows store edition), neither on magix store, nor on Producer planet
I don't think anyone here has had experience of that program.
Normally vouchers given out by Magix automatically show in the store content. If that isn't happening I'm not sure what to do. You should take that up with the Microsoft store. They are the ones offering the vouchers, not Magix.