The connected app or user lacks required permissions.

Problem Explanation

Salesforce enforces OAuth scopes, object access, and IP restrictions on API calls.

Root Cause(s)

1. Missing API Enabled permission

2. Insufficient OAuth scopes

3. IP relaxation not configured

Step-by-Step Solution

1. Verify user profile permissions

2. Check Connected App OAuth scopes

3. Review IP relaxation settings

Edge Cases & Variations

1. Community users have limited API access

2. Named Credentials simplify auth issues

Common Mistakes to Avoid

1. Using wrong user for integration

2. Ignoring permission sets