Post the ones you have noticed being asked a lot here, want to put this up on the WIKI.
I will get us started with what is actually the most frequent anyway.
1 When i hit the pads, sound is delayed or does not play.
You have note repeat turned on.
Here's one that made me waste the most amount of time.
2 Midi input isn't working.
The input source isn't turned on in BM3's settings. Input devices aren't turned on by default, output devices are.