Struggling with "allow_sign_up = false"

We’ve recently configured our Grafana instance [v6.7.1 (ca6d08d5cb)] to use Azure/SSO as the primary authentication mechanism.

We’ve successfully disabled the login form with:

disable_login_form = true

Further reading [link] led us to add:

allow_sign_up = false

but we’re still seeing the “Sign Up” button.

Does anyone have suggestions what we might have missed, misconfigured, or misunderstood?

Answering our own question, we carried on digging and discovered that there was a deployment pipeline that set

essential: true
    value: "true"

in the config for the ECS deployment.

One deploy later and everything looks as we’d hoped.