First of all tell me did you experienced the issue you mentioned before
" when CNG show last green lite after that he started Beeps unless i switch to Petrol. it is not show red lite "
or it started happening after filling gas from some other station?
Normally this thing will happen when your pressure to the CNG injectors is lesser than the required minimum pressure.
The solution is that if you look the cng kit it has a black cap in front of it. Carefully get it off from the kit you will find a screw. Move it counter-clockwise.. just like un screwing anything. But rotation should be 1-2 times.
Your problem of red light not appearing should be solved. If not let me know...