GNSS Problem: AT+QGNSSRD? always returns +CME ERROR: Operation failed

We are using MC60 module, with firmware Revision: MC60CAR01A15. But we are unable to read the GNSS data using AT+QGNSSRD? command, it always returns +CME ERROR: Operation failed. (Although AT+QGNSSC=1 is successful but QGNSSRD fails always).

What could be the reasons?

Hi Trakbond:
When testing, connect the GNSS antenna, and place the antenna outdoors, where the satellite signal is good, and not be seriously blocked. Then check the signal strength, send a log of nmea sentence, and check it. AT+QGNSSRD? Thanks!