Ford Escape 2002 after market alarm

I recently purchased a after market alarm system with remote start plc2 way. It was installed by a professional company. I had to pay separately for the unit and also installation, bypass sensor and key copy. Here is the big problem: Everything works good except remote start. I took the car back to the company what installed the alarm, they reset the bypass sensor, remote start works but in about 6 hours won't work again. Same story, take it back, reset the bypass, works, 6 hours later, it doesn't. I believe that anti-tefth kicks in and won't allow me to start the engine remotely.
I took it back again, being really fustrated and it happened again - in about 6 hours after reset, remote start won't work. Company who installed the system won't do anything to fix it and they keep saying that installation is correct but.
Anyone who can explain and/or help to solve this issue? There is a problem with the system, bypass sensor, anti-tefth or installation? Any help will be greatly appreciated.
Thank you.