From another forum:
The extractor may be too far onto the bolt face. If you look at the extractor hook itself you will see it is beveled. As the bolt closes the case slides down the bevel and pushes the extractor outward, it then pops back out to engage the case rim.
Sometimes the extractor comes too far out and blocks the cartridge. if you look at the bolt face from the front you might see the top of extractor where it is flat. The case can get hung up on the flat surface instead of sliding down the bevel. Use some solvent and clean the extractor, it may take some work if there are brass shavings.
Also check the ejector, that is the plunger in the bolt face itself. Take a punch or other tool and push in on the ejector, it should become flush with the bolt face then come back up when the tool is removed.
Turned out to be something stuck behind the ejector.