OK, so with that setup you should have a (post corrected) PI21 between the antenna and the receiver and the coax from the PI should go to the one input marked SWM (usually input 1) and no other cables will run to the receiver.
You need to get it set to 17 and SWM and go to signal meter and then signal strength. This screen will show the 101 and transponder 1. Move the antenna until you see signals on this screen at least in the 70's but 80-90 would be better. From here you will likely be able to make the necessary adjustments to get 99 and 103 on track but you really have nothing until you can get the 101 in your sights.