I bought p4 before 4 months ago.abd unfortunately i have to faced above mention  case and i handed over my p4 to service station and last time they said they changed few items which import from DJI but today this error massage appear again and plz let me knw what should i do..

Hello abeykoonoff, really sorry to hear about that, may I know have you tried to restart the aircraft or change another mobile device which is in DJI recommended list?
Please check firmware version on "About” page, and then make a screen shot of HD page, thanks.