There are basically two ways of linking registrations to songs using a score managing app on a tablet and a Genos.
There is the 'old' (difficult/cumbersome) way of using patch selects and program changes, which requires a different setup for each direction of linking (direction 1: loading registration causes song to be displayed /direction 2: loading a song causes registration to load)
And then, there is the easy way which allows a registation and a song to be linked
both ways, just by pressing a button (icon) in the app on the tablet.
For as far as I know there are currently only two score managing apps on iPad, that allow that second (easy) way to be used. They are called Songbook+ and Mobilesheets. They use Sysex Midi to make the link. When linking to Genos, I strongly recommend switching to one of the apps that allow the easy way of linking and make things far more easy for yourself.
If you do need to stay with Onsong, there has been a post before about Onsong and Genos on this forum ....
https://www.psrtutorial.com/forum/index.php?topic=44563.0On Genos you may want to use Midi setting 'All Parts' whichever way you decide to go .
Good luck
Rudy