Welcome to the forum.

It sounds like you used the Bb fakebook to determine the key for BIAB. Change the key instead as if you were using a C fakebook. For example, if your Bb fakebook says it's in F, then it's really in Eb concert. You should have chosen Eb not G. Then go to Preferences, Notation. You will see a Transpose pull-down. Select tenor sax, soprano sax or trumpet - any Bb instrument. That will change the notation up a step without changing pitch, so the song plays in Eb but you are reading in F and can play along on your tenor.

If that's not it, and there are a few other possibilities, then write back and give us precise details of the steps you tried.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.