Laravel Passport Password Grant - Client authentication failed

After hearing a lot about laravel passport, i thought of implementing it into my new project where my requirement is to create an API that'll be used in a mobile app.

So my mobile app is a client, which will further have its users.

I followed the steps mentioned by Taylor and also read about it here. In nutshell i followed these steps:

1. Installed laravel/passport.
2. Created a website user.
3. Generated passport keys php artisan passport:install
4. Generated client_id and client_secret using php artisan passport:client
5. Added redirection and callback routes in web.php
6. Authorized the user and got the final access token.

Then i tried calling api/user( with Header Authorization containing value Bearer eyJ0eXAiOiJKV1...(token)

I received the data. Pretty simple and neat.

But my app users won't have these details. So i thought of configuring Password Grant Tokens which fits perfectly in my requirement.

Not starts the real headache. I've been trying yo set this up from the last 3 days and continuously getting

{"error":"invalid_client","message":"Client authentication failed"}

I've tried almost every guide i followed online: Redirection Issues, Add Atleast One Scope Solution, P100Y Issue etc.

But I'm still getting invalid client error. Here's what i'm passing through POSTMAN to oauth/token:

{
    "grant_type": "password,"
    "client_id": "3,"
    "client_secret": "8BUPCSyYEdsgtZFnD6bFG6eg7MKuuKJHLsdW0k6g,"
    "username": "[email protected],"
    "password": "123456,"
    "scope": ""
}

Any help would be appreciated.