This happened to mine....there is a latch next to the boot lock that disables the cable release....christ alone knows why.....bumped mine while putting the sub in and the bloody thing wouldnt open with the key.
My solution was pull the back seat out and theres a (small) access panel, got a mate with long arms and a long pair of pliers to move the switch and it opened with the lever.
Unless your cables broken......then your rooted.