Twirly22

my dad's car won't start - I have tried changing the fuel filter as the vehicle hasn't been serviced for a while - thought that might have been the problem. the battery wasn't the problem either, double-checked it and tried to start the car with 2 batteries yesterday but had no luck. i plugged in my Foxwell i70ll obd reader to see if any codes came up - only about the number plate bulb and the swirl flaps. but I already know about them. if anyone can help, that would be fantastic, thank you.