You say you have a leak, but what is the reason you suspect one? Is it smell? If so, three things come to mind, as the above post says, it is not uncommon to smell propane when a tank is low and about to change over. I have never seen any explanation as to why but it is a real thing which happens.
The second thing which comes to mind is that your oven pilot light has been left on and is out. That small amount of leaking propane is very often just enough to drive you nuts looking for "that smell". Turn the gas for the range to "pilot off" just to be sure.
A third thing is a dead mouse. Yea, I know, not a propane smell, right? But many have experienced a propane leak smell and in the long run found it was a dead critter.