Can't connect My Cloud Using ATT Uverse 1Gig Fiber Service

My Cloud OS 3 Personal & Network Attached Storage My Cloud
5

I am currently dealing with the exact same problem. I have spent hours on the phone with AT&T customer service and WD customer service. No one seems to know what is going on. When I connect the My Cloud 3TB directly to my computer via ethernet cable, device is recognized. As soon as I connect it to the modem, there are no lights on ethernet ports and I cannot find the device on my network (or through internet access). I have opened specific ports that WDC said where used by the My Cloud drive and I have even completely disabled the modem firewall (for a period of time) to see if that worked. Nothing! This is a brand new modem from AT&T (I even had a service man come out and replace the modem - still no connectivity). Any ideas from anyone would be greatly appreciated. I hate the fact that I have very fast network speeds now, but I cannot access My Cloud at all on my network. HELP!!!