Gas and Oil Home Heating Furnaces - Can't reset heat pump breaker

I noticed the outside fan was never running while doing yard work but the furnace seemed to be working fine and I assumed I was just looking at it while it was off. When we tried to use the A/C recently... no cool air. I checked the breaker pannel and the breaker marked "heat pump" was off and would not reset. The breaker marked "furnace" is on and the furnace seems to working fine, although now I'm wondering if its been running off of the heating strips. Any thoughts on why the breaker for the outside unit wont' reset? Thanks.

trips without unit running.................you did not specify............bad breaker. if trips when unit running or at start up, an amp reading must be made to determine the problem. possible causes......bad breaker, burnt wire, shorted compressor, need more info....size unit size breaker. etc