No Authorization Header running da-repairs-oauth-validated

[lnmp4000]

Hi,
I've been struggling to enable OAuth while calling my declarative agent through copilot. No matter what I try, the Authorization header is not present on the request when I debug the Azure function.

Initially I was using the Teams Toolkit to create a new Agent, and selecting the OAuth option when prompted.
I've now cloned this repo and deployed the samples/da-repairs-oauth-validated sample. The same issue still occurs, dropping a breakpoint on line 43 of repairs.ts

    const token = req.headers.get("Authorization")?.split(" ")[1];

reveals the token as undefined because there is no Authorization header.

If I tweak the OAuth registration in the Developer Portal from "Any Teams app" to reference the Existing Teams app (from the .env file)

I can get a prompt to "Sign in to Repairs-OAuthdev" but that button does nothing. When I ask copilot, it confirms I am already singed in.

I'm struggling to know what to try next, so any suggestions would be gratefully received.

Thanks