Unable to get a 3G Lock

@OttoPylot you’re the expert! 

@shanester - why do you have a gateway (modem/router) connected to another router?

Connect the MicroCell directly to your modem, bypassing the gateway, and see if you can make a connection. If you can, then that rules out the MicroCell and points to a configuration setting somewhere in the gateway. Is the gateway a telephony gateway? If it is, it could be configured with SIP ALG which has been known to cause interference with the MicroCell's VoIP capabilities. Even with the gateway in bridge mode you need to make sure that there aren't default settings (NAT, SIP ALG, etc) that are still enabled. Something is blocking the MicroCell from establishing and maintaining the required 24x7 VoIP connection with AT&T.

That being said, I would consider switching to WiFi-C (WiFi Calling) if your phones are WiFi-C capable because the MicroCell service is going away once AT&T begins to dismantle their 3G network for future connectivity (5G, etc). AT&T has already discontinued sales at the end of 2017 because the MicroCell had reached its EOL.

I have Comcrap (Xfinity) cable and I use my own Motorola DOCSIS 3.1 modem connected to a mesh WiFi system (Orbi). However, I stopped using our MicroCell's a little bit over a year ago and use WiFi-C exclusively now.

@OttoPylot 

Thanks for your input. I'm 99.99% sure that the problem is related to the 'new' xfinity gateway.

I love my r7000 router and utilize the openvpn server and dynamic dns capabilities. I also have many other server services requiring port forwarding. This is why I have the gateway in bridge mode.

I do have our iphones enabled with wi-fi calling however, its reliability is not as good as the mcell.

@shanester - the MicroCell does not play nice with elaborate routing configurations so OpenVPN, dynamic DNS etc can cause issues. You need to keep it as simple as possible for the MicroCell. You might want to setup port forwarding to a static ip address for the MicroCell based on its MAC address so that the required four ports are always open and available to the MicroCell.

I'm surprised that WiFi-C doesn't work well for you. Do keep in mind that if you do use WiFi-C, it's best to disable the MicroCell (power off) or place your phones in Airplane Mode to disable their cellular radios. If the phones are able to connect to either the MicroCell or WiFi-C, there will be conflicts as you can't force the phone to preferentially connect to either one. It will connect to whichever one offers the best signal at a given point in time. And as you walk around your house that signal will change and you may end up with dropped calls or poor voice quality.

If you still have issues with WiFi-C, either in Airplane Mode or with the MicroCell disabled, then that's more than likely an issue with your WiFi. Xfinity gateways usually have poor WiFi coverage depending on how big your house is (one story, two story etc) and the building materials. That's why I went with my own equipment so I didn't have to pay the ridiculous "rental fee" and I could have considerably better coverage.

There is nothing that AT&T can do about your MicroCell other than have you jump thru the usual hoops only to have them tell you it's your equipment. They will not, nor will we, help you with troubleshooting your equipment because no one wants the responsibility of messing with a consumers home network in case something goes wrong.

I can port forward 123/UDP, 4500/UDP & 500/UDP to the internal IP of the mcell, but unfortunately I have 443/TCP forwarding to my reverse proxy.

@shanester - you need all four ports to be port forwarded as well as the other router requirements. See my Tech Guide (link is in my sig line). You really should consider shelving the MicroCell and switch to WiFi-C (if your WiFi is robust enough). However, WiFi-C does use two of the same four ports that the MicroCell uses but there is no configuration setup to do, so unless there is something amiss with those two ports, WiFi-C should be fine.

WiFi-C is rock solid for us anywhere within our home (3500 sq. feet) and on our property (0.5 acre). iPhones 8 Plus, 7, SE, and XR (at least I think that's what my daughter's new iPhone is).