I'm having a similar problem.  I had my A3 running well for a few days, then I noticed one of my hash cards was not showing up in the mining page.

Screen shot of what I see: https://imgur.com/HVgZjMm

I tried unplugging all of the cards, swapping power cables, swapping data cables, and changing ports.  Nothing seemed to be able to get the 3rd hash card back on.  Any ideas of what else to try?