Doing a post to create a node using Drupal services endpoint with Postman app
In that  petition you are calling the path user.login, but in services is user/login, with a slash.

Also, maybe you are not preceding the path with the base name of your api (normally is /api). So the url should be /api/user/login. You can see the path in 'Edit' tab, in 'Path to endpoint' field.


I recommend you the module services tools which gives you a page  where you can see the urls of the endpoints. This module contains a submodule called services_definitions, enable it to have this page available.