I am reporting that on my iPhone XS iOS 13.4.1, i was not able to turn on Wi-Fi Calling. The emergency address screen appeared with an auto-populated address and I would accept the terms and conditions and click "Continue". There would be no error. The switch would stay on. Then when I clicked the back button, Wi-Fi calling would show as "Off". So Wi-Fi calling never turned on.
Well I found the solution on the Ting forums. it turns out that the solution was to change my Wi-Fi calling emergency address from "av" to "ave". Then Wi-Fi calling stayed on. This is stupid and it doesn't even return an error message like "wrong address".