Error: "non_field_errors": [ "No active account found with the given credentials" ]

Winter is coming :v I was using this library and after installing and following everything written on the README.md I got the above error.

First I tried with the following config.

Config:

Django                        2.2
djangorestframework           3.9.2
djangorestframework-simplejwt 4.1.3 

And I was getting the error:

“non_field_errors”: [ “No active account found with the given credentials” ]

And the server log was:

Bad Request: /api/token/ [12/Apr/2019 02:52:32] “POST /api/token/ HTTP/1.1” 400 7572

Then I changed to the following config:

Django                        2.1.3  
djangorestframework           3.9.0  
djangorestframework-simplejwt 4.1.5 

And I still get the above-mentioned error. The problem is I couldn’t find mentioned error related anything in this repository!!!

What might be the problem?