Rear ended at traffic lights.

Hi,

So a while back i was rear ended while stopped at traffic lights and pushed into the car in front of me. The car behind admitted liability at the scene to the gardai, but its been months later my car is a write off and the other insurance company still haven't conceded liability merely saying " its still under investigation" the thing is there is cctv evidence of me stopped in traffic with space behind the car in front of me, and me getting pushed forward into that car, but there is a tree blocking the car behind me, but you can tell that i was hit first. Im just not sure why the insurance company wont admit liability. Its so stressful and frustrating and its been months. Anyone have an idea of what i should do?