Insignia 2.0cdti not starting

Hi folks looking for some help if possible. I recently bought a vauxhall insignia 2.0cdti, I got back from an 80 mile journey pulled up outside the garage and turned the engine off while I went to get the garage key. Came back out went to start car and it wont start just keeps turning over. I plugged obd2 reader in and showed maf sensor and pcv sensor, both of which I replaced. It still wont start, on live data its reading low pressure in cylinders. I have replaced the fuel pump, crank sensor, fuel rail sensor, and fuel regulator at back of pump still no joy. The timing marks are all correct so belt didn't jump. Any help would be greatly appreciated. Thanks.