What would cause car to suddenly crank but not turn over

CPS was replaced in February as a result of a OBD 2 code. The car's behavior is puzzling. As I wrote, car was running fine till Sunday--crank but would not turn over. Tried again last night and car turned over fine--ran quite smoothly. Scanned and it's throwing no codes.

Do you still have the old crank sensor? Is the new one under warranty?

No, I don't have the old sensor but the new one is still under warranty. If CPS was bad, I would assume that I would get a OBD code.

NEVER assume........NEEDS to be running before it sees that there is no signal, in many cases. OBD codes are for diagnosis , not a specific part failure always.