User the browser Chrome. Form Workflow Plus is built and tested for Chrome
Don't use multiple Gmail adresses inside a chrome profile or session. Form Workflow Plus may not recognize you with the correct email address. => More info
Never link more than 1 Google Form to a Google Sheet. The add-on will not work.
Don't Start/Run another Add-on working with Form Submit triggers on the same Google Sheet where you run Form Workflow Plus.
You can use our "G Merge Plus: Mail and Doc Merge with Attachments" on the same Google Sheet as Form Workflow Plus. Choose to generate Documents / Emails merges "Every hour" or "Daily". Do NOT generate "On Form Submit". Instructions here
When you type an email address during the approval setup, the address must by grey to be saved. If not, hit ENTER/RETURN on your keyboard.
If you do not give reviewers edit permissions to Form Responses Sheet and protected ranges the workflow will move onto the next reviewer and not update the spreadsheet. Approvals will still be updated on the Dashboard => More info