Please help me from "gps receiver missing" error

hardware: PIXHAWK MINI
firmware: PX4
GC: QGroundControl v3.1.3

I’m quite a beginner.

I installed latest PX4 firmware and have done with calibrations of “Radio” and “Sensors”.
I checked cable connections again and again. However, motors won’t run.

When I checked QGC, QGC showed some alerts: “Critical: PREFLIGHT FAIL: GPS RECEIVER MISSING”. “GPS Status” of QGC sais “GPS Count: 0” and “GPS Lock: None”, but LED of M8N GPS is flashing. Even when I went out, it did not gain GPS lock.

I don’t know what is wrong with my vehicle. Does anybody notice any errors?

Resolved. It was a GPS hardware problem. 3DR gave me a replacement and this error has stopped.