First, try pushing in on the door while trying to open.
Tap/hit the area of lock to see if that helps.
Call a locksmith if you do not want to damage anything.
Drill the key cylinder.
#1 and #4 best options
Look up 'The Lock Picking Lawyer' on YouTube and he will show you just how bad Masterlock are. It is a standing joke. You insert a shim like a feeler gauge between the wheels and feel for the flat. You can also open them by applying a little tension and start with the wheel closest to the opening and turn the wheels until you feel the wheel slacken as it drops into the gate. all his videos are under 3 to 5 minutes, he is remarkable! :>D
https://www.youtube.com/c/lockpickinglawyer/videos
I think yours is the luggage lock in this list. I had one of those, it fell on the a carpeted floor and blew apart!!
https://www.youtube.com/c/lockpickinglawyer/search?query=masterlock%20combination
..
..
To unlock a high security safe without breaking its integrity will be a tough job for you but i guess the following link may provide you with some assistance:http://www.youtube.com/user/harisonkeys?feature=mhee
A few possibilities. First reprogram guest key then dip. If not fixed, load pp and Initialize lock. If not fixed confirm proper operation of pp by Initializing a known working lock. If pp is in good shape, change control board and Initialize. Your problem should now be fixed.