I would check the trapway.
A worker could have used the toilet for a trash can.
If the trapway is clear, it should siphon.
Sometimes you have to pull the bowl and auger from the back side.
I am about to rip out this brand new toilet! We just renovated a first floor bathroom and replaced the toilet with a Porcher Calla II 2 piece. It was highly rated etc...It only flushes intermittently. When the flush works, it's fine. When it doesn't, the water just swirls around and doesn't go down. I have replaced the flapper, made sure the tank water level is at its highest. I have looked at the rim holes etc and there is nothing blocking them. I have plunged. I have poured a couple of gallons of water directly down the toilet and it flushes nicely. I have put the float as close to the flapper as possible so it stays up longer. The other toilets in the house flush fine. It seems as if there isn't enough pressure when the water leaves the tank to force the water out of the bowl. Help!
If there's an obstruction, liquid would pass by, but the paper and waste could get clogged up and slow or stop the flow. this could be a defect, but is more likely something caught. It's also possible that it is caused by the wax ring, especially if you used one that has a plastic funnel embedded in it. Those can sometimes almost literally pinch shut if it is too large, or off-center slightly. Some of them are larger diameter than the hole in the flange.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013
I am calling customer service on Tuesday. The plumber snaked, checked the vent etc...It's the weirdest thing. Sometimes it flushes well, sometimes it doesn't. It doesn't matter what's in the bowl. I think the only thing left to do is get a new toilet.