When I open a Studio One 2 song in studio one 3, the presence instruments are are garbled. How to fix?

When I open a song with presence instruments; drums, piano, etc. in Studio One 3, the tracks are completely garbled. Just a mess of low volume sounds. The other tracks in the song like vocal or live guitar are fine. I really don't want to redo hours and hours of work fixing so many songs... Any help appreciated!