Your rx.py command line is missing the required -T trunk.tsv parameter and without it rx.py. The trunk.tsv file contains the NAC in use by the RFSS, a list of primary and secondary control channels, and a listing of talkgroups (TGID's) to scan or ignore, and etc.
The offset (-o 2500) is usually not necessary, but to begin with, just construct your trunk.tsv and leave it alone until you can take a look at the frequency error in the http console or have verified frequency tuning accuracy by taking a look at the mixer plot.
Bill