yep, clicking is typically a 'bad' battery, or a 'bad' starter or solenoid ...
our Subaru outback recently had the same issue - was the solenoid... if I 'hit it' a time or two, I would suddenly and easily crank. Over time, though, it took more and more 'hits' to get it to work. Replacing it solved the issue.
As for 'low battery power' even though the chassis battery reads over 12 volts... it does happen. A low 'cell' within the battery can give a false reading, for the battery level as a whole, but when the LOAD is applied(i.e., starting the engine), the low cell pulls down the whole battery level, leaving not enough 'umphhhh' to start the 'starter'....
I recently had this issue with one of our HOUSE batteries, one of the Four 6v type...
I found the suspect battery, which had two suspect cells, drained it, filled with distilled water, ran thru a full charge cycle, drained again, and then refilled with battery fluid/acid from the local auto parts store. After running thru a full charge cycle again, overnight, it was back to it's 'old self'... and working properly under a load, which was, in this case, the INVERTER when the fridge or the microwave asked for power.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )