ERR_INVALID_SESSION_ID on Salesforce: INVALID_SESSION_ID / Refresh Token Expired. Root cause: Salesforce session token has expired or become invalid. Common causes: user session timeout (default 2 hours), simultaneous login from different location, IP address change during session, Salesforce org session settings changed, OAuth token revoked or refreshed without updating integration. Step 1: Check Salesforce Profile Policies. Log into Salesforce as an Admin. Go to Setup -> Profiles -> Select Integration User Profile -> Session Settings. Step 2: Modify Refresh Expiration. Change "Refresh Token Policy" from "Immediately Expire" to "Expire after 90 Days" or "Until Revoked". Step 3: Re-authenticate Connection. Inside your Zapier dashboard, navigate to Apps, locate the Salesforce connection, click the ellipsis, select Reconnect, and log in with the updated integration account credentials.