SIP Account Registered, but No Audio.

iOS v.14.7.1
Jami v.3.20
iPhone SE (Gen.1)

SIP account:

<uname>
<password>
SIP Server: callcentric.com
Port: 5060
Proxy: callcentric.com

Account Status:
Enable Account (enabled)
Auto Register After Expiration. (enabled)

My account is listed as "registered" when I check via callcentric's web interface, but when I call *123 or *86 for voicemail, there is no sound. The seconds timer is running. The speaker icon and the microphone icons do not respond. The only thing I can do is get the keypad or hang up.