FID not auto ignite during analysis

Hi, I have an issue with Varian GC-430 FID detector. After injecting a sample, I observed no peak, after thoroughly working, I found that the FID doesn't automatically ignite. When I try to ignite it manully from the software, The detector ignite and a peak appear. I checked the gas flows and found OK. I disassembled the FID and cleaned all its parts but still have the same issue. Also I reconnet the connector on board, for two to three analysis, the FID automatically ignites and then again the no ignition occures. Please advise how I can resolve this issue. Also what is the best time to manually ignite FID after sample injection? Looking forward for a propmt solution in this regard..... thanks you Osaid

Equipment: Varian GC-430