Clarification: Does the engine actually turn over? On the one hand you state that it appears the starter is turning but not the engine but later on you said you did a complete compression test on the side of the road.
If the engine indeed spins and you have no compression at all, I am going to suggest timing chain if the motor has high mileage.
However, I will point out weird things can happen. This exact same thing happened to me on my first car (Mustang) and I had to pull the engine and take it apart. I got it stripped all the way down to the timing chain and discovered the alignment pin on the front of the camshaft had sheared off.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
