Recently replaced my gas block on my ar15 and used the same gas tube. Now my rifle doesnt fire. It's not a cycle issue -- I dont see my firing pin punching the primer...click and nothing... hammer seems ok, and firing pin doesn't appear to be obstructed in any way if I remove the bcg. Wondering if the bcg isnt seated forward enough? Looking at another ar the bcgs appear to be seated the same. Does any one have any ideas? Appreciate it!!

If the gas block is longer in some way or the tube not seated fully, your bcg may be too far toward the rear. The tube may be preventing the bcg from seating forward properly. That would prevent the trigger hammer from hitting the rear of the firing pin properly.

Remove the gas tube

You can pull the bullet out of a live round. Wear earplugs and eyepro. Treat the firearm as if it was deadly. Chamber the "blank" and see if it dents the primer

Take a spent case fired from the same gun. Cover the base and spent primer with light paint or sharpie. See if it will leave a mark

Depending on the gas block, you may need to use a gas block spacer. The spacer takes up the space a handguard cap would. This would push the gas block slightly forward and may correctly place the gas tube if that is what is causing your BCG to be slightly out of battery. Precision Reflex and Fulton Armory both sell one. Would recommend Precision Reflex's part as they made theirs for government contract originally and I have one on a rifle the runs without issue.