Softphone - Getting blocked occasionally

We have a FreePBX 13 system set up with PJSIP. All local phones connect and register just fine. We have it set up so that on certain extensions that multiple devices can register. And occasionally I want to be able to use a Bria Softphone. However what happens sometimes when I turn on the account is it doesn’t want to register due to the firewall on the FreePBX.

Is there a suggested method such as a VPN or other setup that would work better?

I assume that the Bria client is coming from an untrusted IP, have enabled Responsive Firewall? With Responsive enabled, you get a limited number of SIP registration attempts from non-trusted hosts. If the registration is successful, Firewall allows access from the IP to other services, if not the host gets blocked.

Since it is on my cellular, any way to modify the login credentials that would allow it to make it through?

Has anyone tried to connect a Softphone on the Verizon network? I am suspect that they are still implementing network level SIP ALG which would block things.

Any suggestions?