Kent from PGMusic suggested the following for a similar problem in RealBand. I don't know if the same applies for BIAB, but perhaps worth a try.
Is there a file in your RealBand folder called "MaxPluginsToScan.txt"? If there is, please close RealBand and delete that file, then see if the DX plugins then appear.
Might want to look and see if that file is also present in the BIAB folder.