How to reproduce these conditions

1. npm install -g firebase-tools (from "Run Functions Locally" docs)
2. Follow deploy instructions except last two steps (deploying) and don't switch to Blaze plan.
3. firebase serve
4. Open http://localhost:5000 and sign in via Google.

Debug output

Expected behavior

Credit card input controls must appear.

Actual behavior

I see ellipses and nothing happens.

Update

This issue feels more like a Stackoverflow question, I should have posted there instead. I apologize if my issue isn't appropriate here.