Only chain #3 is detected and I'm hashing 276 gh/s.
When I setup the miner I had all 3 detected and hashed for about 15 minutes. Afterwards, the asic was showing only 1 detected. I've tried restarting, reseting, changing power supply cables, and changing power supplies. I even tested all power supplies and they all work.
Is there anything I can do before sending it back?
Sounds like its dead, probably a good idea to start warranty claim process with bitmain.
Other than that, the only other thing you can check: make sure you're using a good 1500w+ PSU, if you were using less than that you may have damaged the miner or the PSU failed to provide adequate power and it damaged itself.
If you continue using it, I recommend you drop the frequency to 525mhz from the default of 600 as it seems the A3's run way too hot unless you got some great cooling.