there could be multiple reasons for that .
-The access point have the mac filtering activated .
if that is the case then you must put airodump-ng watching the AP until yoy get a mac connecting to that AP successfully , after that you change your mac to...
-The access point have the mac filtering activated .
if that is the case then you must put airodump-ng watching the AP until yoy get a mac connecting to that AP successfully , after that you change your mac to...