If you have this message, you must add a new form to your project. The steps are below.
To create a form for Clash Detection
Go to the Administration Tab > Manage Forms
Select the blue "+New" button at the top to create a new form.
Fill in the Name, Prefix, Type, and Design Template
You can give it any Name you want up to 22 characters.
The Prefix can be any combination of letters up to 4 characters to identify the form.
You will need to select "Clash" as to type to work with the Clash Detection workflow.
You can select any existing form in your project as the template for your new form.
Flow link for creating forms and all the settings.