Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Are the latches (or, round 'bars' on the door) extended, still?
If so, try using the hand-latch or handle, to persuade them to the 'open' i.e. 'in' position, just after entering the code correctly and the instant you get a green light (and, if you listen carefully, there ought to be a 'click' inside the door, also.)
Put the safe back in the normal position, of course, with the door facing front. Far be it from me to disparage the design of Sentry Safes, but they are probably meant to be oriented that way, for the inner mechanism of the latching inside the door, to work properly.