The access token or session ID has expired or is invalid.

Problem Explanation

Salesforce API sessions expire or become invalid when reused incorrectly or when IP relaxations are misconfigured.

Root Cause(s)

1. Expired OAuth token

2. Incorrect login endpoint

3. IP restriction mismatch

Step-by-Step Solution

1. Re-authenticate using OAuth refresh token

2. Verify correct login URL (login vs test)

3. Check Connected App policies

Edge Cases & Variations

1. Sandbox tokens don’t work in production

2. JWT flows require correct certificate setup

Common Mistakes to Avoid

1. Hardcoding session IDs

2. Mixing sandbox and prod credentials