400 error when logging in when using email only mode.

I am trying to set up authentication using django-rest-auth and django-allauth. The user exists in the database and I can login to the django admin site. When I try to login using the rest-auth/login/ endpoint posting email/password, I receive a 400 error with the following response:

{
    "non_field_errors": [
        "Unable to log in with provided credentials."
    ]
}

I followed the instructions here: http://django-allauth.readthedocs.io/en/latest/configuration.html#configuration

In my settings file I have the following:

ACCOUNT_EMAIL_REQUIRED = True
ACCOUNT_UNIQUE_EMAIL = True
ACCOUNT_AUTHENTICATION_METHOD = 'email' 

If I comment out the three lines above and use the same endpoint but add the username it works. It seems to only not work with email only mode.

Thanks for your help!

[genomics-geek]

I left out AUTHENTICATION_BACKENDS in settings. That was the issue.

[SpeciesDecipit]

AUTHENTICATION_BACKENDS

Oh my. @genomics-geek thank you very much, I have spent about 1.5 hours to try to fix this problem. I do not think that moving from JWT to Bearer Token will so long in the new project. Thank you again.