I just built my ar15 with an 80% lower and it is not allowing me to fire consecutive shots, it is one shot at a time.  My Father and I built the same rifle and his is working without issues.  I fire and it puts another round in the chamber, but my trigger is frozen.  It will not fire or move.  I eject the round re-cock the gun and it fires, but then the trigger freezes up again. I am a beginner to the building and the ar15 so before I dive into it without knowing what to look for, can you give me some direction where to start first.
thanks for the help
Ace

Hard to diagnose without pictures or more description or something.

Problem with the disconnector spring, either upside down or missing completely.

Vince

Ok I will check the spring.  I payed extra attention to it when I put it in.  It cocked and fired without the upper on.
thanks
ace

It's an issue with your trigger reset. With the upper pulled, cock and release the hammer. While keeping the trigger pulled, pull the hammer back to its maximum extent- it should lock back. Then, release the trigger- the hammer should come forward, at which point the weapon is ready to be fired. If this process does not work, you have a problem in your FCG.

i had a similar issue. It SEEMED like I had to charge it again, but really I just needed to push the trigger forward... it just so happened that charging it also allowed the trigger to move forward. In my case it was the trigger spring. New spring=no more problems. 

I have also heard of people having a lower whose trigger hole is slightly narrow, so the trigger rubs the sides of the hole... this increases friction to the point that the spring isn't strong enough to reset the trigger. This is also sometimes the result of a coating (cerakote/dipping, etc). The solution is the pull the trigger group out and sand the sides of the trigger hole in the lower until the trigger clears without rubbing. 

Hey all, first post.  I had the same problem you appear to be having and after reading a lot of helpful info here I swapped out all springs and that didn't fix it.  I finally took a file and lightly filed the points where the hammer and disconnector touch...problem fixed.  I had read about burrs being a problem but mine wasn't so much a burr but just and overly sharp edge.

To anyone who reads this, be very careful doing this and it's best left to someone who knows what they are doing in most cases. Don't just start taking metal from the contact points of your trigger in hopes it fixes a problem you're having.

Yeaouch, that's a dangerous game to play as a noob.  Swap springs and parts, sure, but I would not start removing material from parts without a very good understanding of how everything works.