1--- UNLOAD the firearm ----
Look in the ejection port, and slowly bring the bolt rearward, while watching for the ejector finger to appear in the groove-face of the bolt.....
Make sure the finger is as tight to the bolt center so it get maximum contact with case (which is not much, so you need all the contact you can get).
Double check extractor roll pin, I assume it (bolt) is COLT, as some have reported use of sub-standard roll pin or incorrectly set, not holding extractor proper. I have Garrison, it is fine.
With upper seperate from the lower, drop a live round in the chamber, and close the bolt. Look and see if the case face is flat to the face of the bolt, if not, may have headspace issue, mine did (custom barrel),, had to do a little lathe work to get it to where I wanted it.