When you say you "tried everything", did you power-it down completely, wait at least 30 seconds and power it up again?
OK, so suppose you did that and it's still in the alarm mode. Now power-it down again, but this time when you power-it up again, do so only while continuously pressing the "P" and "Cancel" buttons on the control panel. Once it's fired up, let go of the switches and see what condition it's in.
You may have to clear it and go through one more off/on cycle to get a full reset.
Oops, I just realized that your original post was on the 23rd of the month. Presumably, it's already running again. What was it? How did you reset it?