Niiice! I like the Krinkov-style top cover.
Are you using the standard-length recoil spring or did you cut one down? You might have too much spring for it to cycle reliably. If necessary, you can wind a replacement from thinner music wire wrapped around a dowel.
Are you sure the hole in the gas block is properly aligned with the one in the barrel?
Is the gas piston going far enough up into the gas block? As long as it's not bottoming out inside the block, you might try fitting a washer between the back of the piston and the bolt carrier. The longer stroke would provide more kick to the carrier.
How far back does the bolt carrier travel when it's working correctly? A small chunk of modeling clay on the buffer will tell you. Don't use too much; you don't want to bottom the carrier out on the clay.
Do you have access to any other ammo? You might have a bad batch, or some that's mixed from more than one batch.
I don't know if it's a valid test, but I removed the hammer and recoil spring from my AKM while I was fitting the side rails, and decided they were good enough when I could point the muzzle down, let go of the bolt carrier, and the rifle would go into battery with no urging. My ejector was binding the bolt when I started, and it took a little grinding to get everything to clear properly.