4a) Brain: cable plugged into appropriate plug? Some PBs have two external serial connectors, some just one. In case you put an internal modem into a PB160/180, the external modem port gets disabled.

4b) Brain: StyleWriter does not like AppleTalk too much. In case you activated AppleTalk for the serial port the StyleWriter is attached to, it is most likely not operational (except you use an AppleTalk bridge attached to the StyleWriter).