MongoDB works only on user is assigned to admin database

I am using mongo db with authentication and it is working as expected when I map the user to the admin database like below, use admin; db.getUsers(); { "_id" : "admin.test1", "userId" : UUID("abee0e0c-1d0b-44fa-84ad-594159b66aab"), "user" : "test1", "db" : "admin", "roles" : [ { "role" : "readWrite", "db" : "test_database" } ], "mechanisms" : [ "SCRAM-SHA-1", "SCRAM-SHA-256" ] } I am able to connect to the database using 'test1' user and access the 'test_database' but when I create user with actual test_database, It is not allowing me to connect, use test_database; db.getUsers(); { "_id" : "test_database.test2", "userId" : UUID("abee0e0c-1d0b-44fa-84ad-594159b66aab"), "user" : "test2", "db" : "test_database", "roles" : [ { "role" : "readWrite", "db" : "test_database" } ], "mechanisms" : [ "SCRAM-SHA-1", "SCRAM-SHA-256" ] } When I connect using the 'test1' user to connect 'test_database', I am able to connect and It is working as expected (weird how the admin database access helps 'test_database' though) - why? but when I connect using the user 'test2' it fails with the following error **pymongo.errors.OperationFailure: Authentication failed.**