I didn't read all of the post thoroughly above, so if I repeat something you have tried, just ignore it.
You have checked to make sure the cases are not too long? Trimmed to correct length?
Will a resized case chamber if there is no bullet in it? And not close if a bullet is seated? This could be the neck wall of the brass is too thick which could be very dangerous if you were able to get it to chamber causing excessive pressures as it doesn't have enough room to release the bullet if the chamber neck is too tight. If you have a caliper, check the outsize diameter of the case neck on a resized case and on a factory case and compare. If the resized case is larger, that could be the problem.
Have you tried calling the die manufacturer? They are usually a big help.