This error usually means the Salesforce user connecting the app lacks permission to authorize a connected app that isn't installed in your org. A Salesforce admin can fix it by assigning the Approve Uninstalled Connected Apps permission.
Why this error appears
Salesforce restricts access to connected apps that haven't been installed in your org. When a user without the right permission tries to authorize such an app, Salesforce blocks the OAuth connection and shows this error.
The fix is a permission change in Salesforce, so it must be made by a Salesforce admin.
Solution: assign the Approve Uninstalled Connected Apps permission
Assign this permission only to trusted admin users who need to access apps that aren't installed, for example during troubleshooting or in specific integration scenarios. Assign it through a permission set:
- From Setup, in the Quick Find box, enter Permission Sets, then select Permission Sets.
- Open an existing permission set, or click New to create one.
- Click System Permissions.
- Click Edit.
- Enable Approve Uninstalled Connected Apps.
- Click Save.
- Assign the permission set to the user who is connecting Salesforce.
Reconnect Salesforce
Once the permission set is assigned, return to our app and connect Salesforce again with the same user. The authorization should now complete.
If the error persists:
- Confirm the permission set is assigned to the exact user you're connecting with.
- Log out of Salesforce, log back in, and try again so the new permission takes effect.
- Check that the user's profile allows API access.