NSS7  with Idirect Netmodem II plus

Is your wanted iDirect carrier on the same downlink receive polarisation as the carrier you have detected at 3931 MHz ?

If not, note how the OMT is presently attached to the polariser.  The OMT is the joint where the 4 and 6 GHz rectangular waveguides merge into a circular waveguide.  To change polarisation you will need to unbolt the OMT from the polariser, rotate 90 deg and reattach in order to receive the opposite circular polarisation.  The two attachment positions will be +/- 45 deg either way from the line of pins inside.   If you align the OMT waveguides the same as the pins the polariser have no polarising effect and you will be operating linear polarisation, which I doubt what you want.  If you are receiving circular polarision with a linear feed you will get severe interference if there are carriers on the opposite polarisation and just 3 dB loss everywhere else.  This could be your problem.

This page may also help:
https://www.mmtelcom.com/webdex/Tech_support.html

Note you need to input your lat/long and satellite location and elevation angle.  It says this is critical (in red).  It is possible that the software blocks transmission unless you have done this.

If you solve the problem please tell us for future reference.    Thanks, eric@satsig.net