Without a lot more information from you we, fellow-users have next to no chance of being able to help you! At the moment we know nothing about your computer, nor even about the exact version and variant of MM which you have!
So, please tell us a lot more!
Just for your information: I'm running the latest version of MM 2021 Premium and the Song Maker is very much still present!
Search for Song Maker to see more threads about this.
I suspect that you have installed MMM2021 but purchased MMM2020 Premium or a previous version. Song Maker has been completely changed in MMM2021 and the only way to get it is by purchasing it in the Store or by purchasing Plus or Premium for 2021, not 2020. See the comparison table on the Magix.com website.
To keep the old version, you should have selected keeping the previous version of Music Maker when you installed MMM2021.