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.
Anything optimistic you can do to help ? Give me some hope.
Check your PSU, if it's a good 1500w+ PSU and its working fine the only thing you can do is power cycle the miner and hope it comes back.
If you used an underpowered PSU or a low quality PSU, unfortunately there isn't much hope based upon what you've reported so far.
evga supernova 1600w p2. Is there any custom firmware for the a3?
Good PSU, but I have had one of those fail on me in the last year so make sure you check it with something to see if its actually working.
No custom firmware that I'm aware of, these things were a surprise release to the world less than 10 days ago.