I believe to get things to work properly, you must set all your extenders to Fixed IP address in the Pronto Project. It must be on your network and have a valid IP address and it is that fixed IP address that you should set in PEP2/PEP3.
For sure, it will not work with an RFX9400 that is in ad-hoc mode (ProntoNetwork1, .. ProntoNetwork3).