Engine cranks but will not fire

Chronic problem over the last couple of months took it to a Toyota dealership they put in a new battery said everything was fine. That worked for a couple of weeks and then the problem came back. My local mechanic is very good sprayed some starter fluid and it fired right up. Car ran fine after that no hesitation did not shut off at idle. Problem came back starter fluid no longer worked. The the latest indicator that popped up is that when I try to turn the engine on I get a clunking sound and it will not turn over. Then I tried it again the engine turns over but still will not fire.

I thought this might be the crank position sensor. But not sure because I think this will be indicated by the engine shutting down when idle or hesitating. Does none of these.

Could it be ignition relays? We really can't figure out at this point. Any help would be greatly appreciated.