SIM808 GPS " UNKOWN LOCATION" need help!

hello, I bought a gsm gps sim808 module and I noticed that the led of the gps does not light up despite that I test with the at commands for the command AT + CGPSPWR = 1 or AT + CGNSPWR = 1 and j I have as an answer OK except that the gps led never turn on and gps status always shows me “unkown location” I check the power supply and the operating condition of the gps( I put it outside for an interval of time) but no result can you help me