Microcell doesn't work anymore

If you have the iPhone 6 or newer (you do) you should try turning wifi calling on, and deregistering the phone from the microcell.  

Did you try wifi calling when you got the 6s?

Yes.  Has her phone been working on it okay?

With wifi calling feature the newer iPhone may not be compatible with the microcell. 

Helpful information.

https://www.att.com/esupport/article.html#!/wireless/KM1063258

https://www.att.com/esupport/article.html#!/wireless/KM1100375

@DeuceB

There is no 4G/LTE version of the Mcell.  Both the DPH 151-153 (white models) and the DPH 154 (black model) are 3G-only devices.  All will connect to 4G/LTE phones but only using 3G protocols.  Not sure where you got the idea that the DPH 154 connects with phones using 4G/LTE protocols, but that is incorrect.

@Dneiman25

A few questions/suggestions:

1.  One-way communication is typically an ISP line-quality problem.  You should run the speed test and VOIP quality tests as outlined in Otto's Tech Guide and report the results here.  The VOIP tests should be run at several times during the day to check the variability of your connection as that can change depending on the load on your particular cable node and a variety of other factors.  TWC seems to have more than their fair share of line quality issues.

2.  Have you changed any of your home network equipment (modem, router) during this time? 

3.  The Mcell will always have priority over WiFi-Calling on a given phone unless that phone's number is removed from the Approved User's List for the Mcell.

4.  The indicator light symptom you described in your last post makes me think you should check out your Mcell's AC adapter for the proper output voltage using a voltmeter.  The procedure is outlined in the Tech Guide.  The output voltage of the adapter should be 16 VDC +/- 0.5 VDC.  If it is not within that tolerance, your Mcell may act wonky.  Replacing the adapter with one of the EXACT same output as the original adapter would be a good troubleshooting step to take.

@DeuceB- the new MicroCell, the black DPH-154, will work with any AT&T 3G/4G/LTE hand set, but still only has a 3G radio, it is not 4G. The same is true for the older, white DPH-151/153 models.

@Dneiman25 - if your MicroCell is that old it could be as simple as a failing ac adapter. We've seen all kinds of odd things happen when the adapters start to fail. A simple check is to check the adapater with a voltmete. It should read 16VDC +/- 0.5 with no load. If not, replace the adapter with one of the exact same power rating and see what happens. If you were sent a new MicroCell (DPH-154) hopefully AT&T also sent a new adapter with it as well. They are slightly different and it's always best to use the one that designed for the model of MicroCell.

Call quality issues are most often related to the ISP (bad switch, maintenance, firmware update, line quality problems, etc). That's not to say that it couldn't be the MicroCell but experience has shown us that quite often it's something else.

If the 3G light starts to flash green (the top most LED indicator on the black MicroCell) then you have lost connectivity to the AT&T Mobility servers which obviously will affect your calls. That to me indicates a routing issue.

@lizdance40 - if he attempts WiFi-C (WiFi Calling)  he will need to do more than de-registering the iPhone 6 if he still needs to use the MicroCell. With an active MicroCell, the iPhone 6  will need to be put into Airplane Mode to disable the cellular radio. If not, the iPhone will attempt to lock onto the 3G signal from the MicorCell but won't be able to because the phone number has been removed from the MicroCell. This is by Apple design. The phone will preferentially attempt to connect to a cellular signal over WiFi. WiFi-C is similar to the MicroCell in that it is designed to fill in gaps of cellular coverage. It is not intended to be a full-scale replacement for cellular calls. Either disconnect the MicroCell altogether (power off) or enable Airplane Mode on the iPhone 6 and enable WiFi Calling. As a side note, WiFi-C on AT&T's network uses two of the same four ports that are required for the MicroCell. So if there is something affecting those ports, there may be issues with WiFi-C.

I have an iPhone 5SE, the latest iteration of iPhone, and there are no compatibility issues with the MicroCell. WiFi-C works just fine with my phone in Airplane Mode. WiFi-C works fine with the DPH-154 and the older DPH-153. All I had to do was install a new SIM card in my 5SE because my old SIM card for my iPhone 5 wouldn't allow me to do WiFi-C (provisioning for HD Voice).

Do you have time warner cable and an Arris modem?  That's my combination. Everything was fine for a few months and then on the same date you submitted your topic, 25 July, that's when we lost connection (top most LED blinking)