Problem with Link to Authorization Page

[TrevorJDaniel]

Hello,

I have a website with a link to the Authorization page that has been working pefectly for months. And, now, for some reason I don't understand, has started displaying strange messages.

My link to start the authorization process looks like this:

https://www.fitbit.com/oauth2/authorize?response_type=code&client_id=227N6Q&redirect_uri=http%3a%2f%...

This successfully takes the user to the sign-in page. But as soon as the user has entered their username/password it throws the error show in the image below...

Does anyone understand what might be going wrong please?

Any help would be greatly appreciated.

Trev