Will not start, possible low compression

Piston rings do not just all of a sudden go bad, especially not all of them at the same time. You would notice gradually the engine loosing power over weeks or even months and/or smoke coming out the tailpipe such as light blue smoke.
I would first make sure the engine had coolant in the system and motor oil if either is really low then that might tell me where to look next.

No coolant the engine bearings could seize the engine up if the engine got too hot or the pistons could have expanded too much and seize in the cylinder. Check the overflow coolant tank or the degas bottle for coolant.