Ann,
As it is just possible that your safe is unlocked but jammed, I have another suggestion. Timbo recommended penetrating oil and a hammer. When a door is immovable like this I suggest that a heavy hammer be forcefully applied directly to the door plate at a point exactly half way between the hinges while applying as much pulling power as possible to the handle on the opposite side. It may take quite a few blows but any progress will be observed around the leading edge of the door.
I have a feeling though that it is still locked. My reason for saying this is that when opening this model, after unlocking, the handle is turned a full 180 degrees from 6 o’clock to 12 o’clock. In its present position it means that the main boltwork is still fully extended. The reason for the unusual unlocking movement is because the boltwork is operated by a brass cam into which the bolt of the keylock operates. Incidentally, Chubb incorporate hardened drill-resisting studs in the area surrounding the lock.

The foregoing is based on experience from the distant past but I have bad memories of having to undo the more than two dozen screws around the lockcase to access the lock.
John.