Anyone got any ideas ?
I suggest connecting via OPlink and check what GCS says about number of satellites. Just go to scopes, change one of 4 scope views to GPSSattelites->SattelitesInView or GPSExtendedStatus -> Status. Also in System you should see GPSDisplay widget with Sats Used (this is different from sats in view) and what types of sats are seen.
Have you checked
https://librepilot.atlassian.net/wiki/display/LPDOC/GPS+setup ? For Revo you don't need to set anything on GPS, but GCS side it should be correct protocol and port.
Can you even communicate with GPS ?
OP GPS v9 has three ports, one is gps+mcu which gives mag+gps data, but another port gps gives raw ublox stream. So you can use that port to connect to it via Ucenter from Ublox and check configuration and visable sats. Of course you would need usb-serial converter 3.3V level.
My GPS and others work just fine, so it's unlikely it's something with firmware, I would check wiring, if its right port, hardware wise, can antenna see clear sky. Sometimes it helps by turning vtx off to get lock a bit faster, but it never prevents from getting lock at all.