I face this kind of problem when I use Soundpool DVDs. I got MMM 16 Premium.
I have added here a screen shot that can show available Soundpool styles and also in Songmaker. Soundpool styles markes as green and Styles in Songmaker marked as Red 1.
I have added green marked image on songmaker screen shot for reference only do not get confuse please.
As your question is not clear, I guess you want to have all styles in songmaker right?
How I solve problem like yours?
When Magix Music Maker is open on key board press "Y" Program settings will be opened under General Tab, look at right bottom you will find "Reset Soundpool and Clean up Soundpool" I prefer to click Reset Soundpool it will remove all soundpool then Clean up Soundpool, by this way soundpool and instruments are removed. Now I have to use Add styles button to re add Soundpool. This method helps a lot when I face problem.
For Soundpool problem and solution you can read my pdf with photos.