"Remote Access Application Authorization" Salesforce Exception

1. If you are using custom domain, use the custom domain instead of using login.salesforce.com for production or test.salesforce.com for Sandbox.

2. Check whether the profile have "API Enabled" permission.

3. Go to the User Detail page of the user and check whether their account is locked. If yes, unlock it to resolve the issue.

4. Check the Login History for login failures.