I have the same problem. I have a two-way though. but same thing. when you key-on your car, look in the dash for the little green key light. if it flashes in interval, your car doesn't recognize ether the key or the FOB. start by changing the battery in your FOB, remember to always lock your car. that should avoid the Immobilizer problem. if problem persists, get a new chip key cut for your car.
depending on your car, the immobilizer you have does have a 3-5 min downtime. get out of the car lock the doors, walk away (this triggers the immobilizer because your not with-in 15 feet of the car) and come back in 5 mins unlock and start. this works for me every time. Save your car battery look in the dash if the green key light flash then Repeat process. it sucks i know.