You probably have not set the MIDI channel on your MIDI keyboard to channel 1, 2 or 3 for addressing one of the B4 manuals. Logic directly forwards the keyboard's MIDI channel to the plug-in independently from your track settings. You can see the MIDI channel of each single note you record in the Event editor of Logic. If you can not set your MIDI keyboard to a suitable MIDI channel, you can also use a keyboard split in the Key Split menu of the B4. This will cause the B4 to receive MIDI on all MIDI channels (Omni).