Ideally, you should leave the pitot hooked up as it is. Pull the tubing off of both of the sensor board ports. Blow through the front port (Port 1) of the pitot tube with your mouth and make sure it is clear. It does not matter if it is a little pinched, as when the system is running, there is no air flow going through the tube, only pressure.

Take the tube that you heard the air coming through and connect that to port 1 of the sensor board.
Leave port 2 open for now.

Turn on the system and then blow on it again. If it is still not indicating, then call Bob to make sure I have not missed something obvious. He will take care of fixing it if needed.

The difference between a 4 and a 5 is a hard plastic case. The reason I asked is that I am not familiar with the 5.0 and I would not know if I am missing something with a 5.0.

Good luck,