Mine screwed right in too….no issues. I’d start the troubleshooting process by checking to see if a 3/8-16 bolt screws in to the tie-down.
 
General question about tie downs rings:

Mine are from Vans and seem too long. They will not thread in all the way. I'm reluctant to force them but the bending moment will be higher if I can't screw them down. Is this normal?
 
I had to tap my tiedown mounting blocks a little deeper after they were already installed, not really a big deal if you're careful.