REST API for 4.0.2 not working

Your software
My Mautic version is: 4.0.2
My PHP version is : 7 (Laravel 7 framework)
My MySQL/MariaDB version is (delete as applicable): MySQL/MariaDB version

Installing Errors
*I am new to mautic : Installing
*Upgrading/installing via : Command Line (VS code IDE)

My problem is :

postman test for : https://Domain/api/contacts?code=CODE

"errors": [


        "message": "The access token provided is invalid.",

        "code": 401,

        "type": "invalid_grant"




please help me to add contacts from database and also to retrieve from API