Did you get the problem resolved?

2018 Band-in-a-Box for Windows added support to export as a MP3 file. Here is a quote from the 2018 new features page:
Quote:
Songs can now be saved as MP3 files in high resolution. M4A song saving has been enhanced and is faster.


Jim Fogle - 2024 BiaB (1111) RB (5) Ultra+ PAK
DAWs: Cakewalk by BandLab (CbB) - Standalone: Zoom MRS-8
Laptop: i3 Win 10, 8GB ram 500GB HDD
Desktop: i7 Win 11, 12GB ram 256GB SSD, 4 TB HDD
Music at: https://fogle622.wix.com/fogle622-audio-home