Keep/Safe 7100 wall safe - known combo wont open
I have a Keep/Safe 7100 wall safe that will not open. I have the combination and have opened it within the past year, however, I can't open it anymore. This safe does not have a handle, after entering the last number of the 3 digit combo, you need to press the upper left hand corner to open the safe. The dial does seems a bit harder to turn than what I expected, but I have little to compare, so this might be normal. I was hoping someone might have some insight on why it won't open... Can anyone explain how pushing the upper left corner opens the safe ? Is there a diagram that would show the mechanism.
Thanks in advance for any assistance
Mike