Login with google authenticator gives 400 bad request

I have an Angular2 app with a custom login UI. Using the auth0 js library I call the loginWithCredentials method passing in username and password.

If I disable google authenticator in the dashboard the login works just fine. If i enable it from the dashboard when I login to my app I am prompted for the code. When the code is entered I am redirected to a https://{mydomain}.eu.auth0.com/mf page showing a tenant is required error.

I had this working last week but something is now causing it to fail and I’m unsure if it’s something I have done in my client, my auth0 config or a change in the service.

The chrome developer tools report HTTP 400 (Bad Request) for the POST to the https://{mydomain}.eu.auth0.com/mf page.

Confusingly this now works again today with no changes my end.