Changing MS Basic to Muse Sounds in 4.4

I just installed MuseScore 4.4. The sounds are all MS Basic, and when requesting a change to Muse Sounds, I have a panel opening that asks about Muse Sound percussion (when clicking on any instrument) and it appears that Muse Sounds is not selected at all. How do I manage to get the Muse Sounds to become selected?

Many thanks

I also noted when playing back an existing score from 4.3 that the dynamics appear to be affected. The trombone in an orchestra score is now way too loud, I have to change mf to p to approximate what I had before.