“The REST API is not enabled for this Organization” while using Salesforce REST Api

Check on the profile for the user. Access the profile settings in order to verify that API is enabled as well.

  1. In LEX, go to Set up | Users | Profiles. In Classic, click Setup | Administration Setup | Manage Users | Profiles.
  2. Select the profile that you need to check, and under “Administrative Permissions” verify if API Enabled is selected.