You must enable Send Back to Requester on Form Workflow Plus sidebar Advanced tab.
Send Back to Requester is used to:
- inform the Requester the status of their workflow request at the end of each Approval Step. If the workflow request needs to go through to another Approval Step the requester is notified and should wait until all Approval Steps are completed.
- allow the Reviewer to send a workflow request back to the Requester for revision
To be able to Allow Send Back to Requester, please ensure you choose Collect email addresses on your Google Form