If you are using the SynthMaster version that came with Band-in-a-Box, it should not require a key. If this is the case for you, try doing the following:

Close Band-in-a-Box and go to this folder directory: C:\Users\<username>\Documents\SynthMasterPlayer
Rename or delete the following two files:

Config\SynthMasterPlayerConfig.txt
synthmasterplayerlicensekey.txt


Andrew
PG Music Inc.