Error while updating to v3

While trying to update to version 3 of the api, I am getting an error.

When I send this URL to generate access token

https://authz.constantcontact.com/oauth2/default/v1/authorize?client_id=edf8807c-1f10-430a-954a-45e84e396ed6&response_type=code&redirect_uri=http%3A%2F%2Flocalhost%3A3000

I receive this:

http://localhost:3000/?error=invalid_request&error_description=The+authentication+request+has+an+invalid+'state'+parameter

Thanks!