ATT Microcell works with one iPhone in the house but not the other

Question

A client of mine got new two new iPhone 6 phones when he and his wife signed up for ATT service. What ATT failed to tell him is that they don't have a tower in the area where he lives and he gets no cell reception from his house, and has one bar while standing in his driveway. Extremely frustrated, they went back and complained. ATT's answer (of course) was to then sell them a Microcell device. Oddly the Microcell they received is a small black box with only a single ethernet port in back. It is not like the white 'Y' designs you see online. The whole thing seems like a money making scam to me but that's beside the point. Anyway, I went over and hooked up the Microcell to their Xfinity router from Comcast, then logged into their ATT account and initiated the activation process. It took about 30 minutes to complete all four stages which included downloading a software update. Once the Microcell was activated, one of the Iphones had full bars. However, the other iphone still only had a single bar. Why would one iPhone have full bars and the other still have only a single bar?  1. Tried turning off both phones and turning them back on. Problem persisted.2. Tried moving the phone with a single bar coverage right next to the Microcell. Problem persisted. 3. Tried turning off just the iphone that had full bars. Problem persisted.4. Tried resetting the Microcell device. Problem persisted.5. Tried disconnecting both phones from the wireless internet network for the house. Problem persisted.  Really confused on this could be happening with just one of the two iphones in the house.

Answer 1

AT&T has not completely updated the MicroCell page and links. The new MicroCell is the black DPH-154 model which is replacing the white "Y" shaped models and you describe it. Functionally, they are currently the same. The only difference is that Cisco/AT&T has done away with the external antenna port and the Computer port. It's not a money making scam.
You can have multiple phones connected to the MicroCell at any one time without issues. One of the iPhones I assume has the phone number that is associated with the AT&T mobile account. That should be the phone number used to register the MicroCell with (what we call the primary number). The other iPhone, which I will assume is on the same account, needs to be added to the Approved Users List. Once you add the "problem" phone, turn off the phone and then turn it back on so that it can add the MicroCell to its cellular neighborhood.