If you get the message below when trying to add a reviewer to your workflow, please ensure the spreadsheet owner has not prevented you from adding new people.
Form Workflow Plus will automatically add reviewers as editors on the spreadsheet. If the spreadsheet owner has prevented editors from adding new people you will not be able to add reviewer(s).
Use Case 1
User email@example.com creates a Google Sheet and shares it with the company's workflow creator, firstname.lastname@example.org, but in the process prevented other editors from adding other people to the sheet:
When user email@example.com opens the sheet and activates Form Workflow Plus to specify conditional approvals/add reviewers, the following error would come up:
To resolve this, the spreadsheet owner would simply need to update the settings making sure editors can change access and add new people to the sheet, as shown:
Use Case 2
Form Workflow Plus worksheet is in a Shared Drive
Make sure reviewers are granted Manager status on the shared drive to allow these to be set via the add-on, as shown:
Otherwise, an "email address can not be added" error would appear when setting the reviewer email address.