Actually.. facing even the reverse. Now 4G logs in and works fine, but LTE indidates voip service unavailable. Very strange. Not finding a common denominator other than the app was recently upgraded. Reluctant to bounce the SBC.

I use 6061 on the outside of my SBCs. It's like some carriers steal 5061 at the kernel level of the mobile OS.

Had a remote worker on my wifi and traceSBC from outside showed SIP register to the SBC from my carrier's data public IP even though I was on wifi and then my PPM failed because the request was coming to the SBC from my internet provider's public IP

Something about Android/modem firmware/whatever was hijacking any outbound traffic on 5061 and using the cellular data network rather than the wifi connection I had enabled. As soon as I used 6061, everything's fine on wifi or on cellular data.

That, and maybe some nasty IPv6 to IPv4 natting on your carrier side. Does your trace show you coming from outside on 10.x? :p

Where is that 6061 change made on the SBC? Just polking through all the screens it looks it can be in a number of places. Then it would have to be open on the firewall. Then I assume the client/app has to be set to use server port 6061.

Really weird issue (aren't they all). There was an iOS update not too long ago, along with a recent app update. Weird how on certain carrier networks it works and then doesn't.

Just for kicks, traceSBC and watch them try and register. Get them to google up "what's my ip" on wifi and LTE and see if you got the same thing I was saying.

Re: SBC, it's on the signaling interface that you define the flow.

Pain is that it's all mapped across inside/outside/in SM etc so you'd have to change it on down the line to have them work fine with "sip.cmopany.com:6061" outside to the SBC and inside to SM. If that's in fact what your problem is. It's one that had me second guessing myself for a bit.