Hi @samsam ,
The Form is usually in Edit mode by default, and Edit mode requires an item to edit - without it, you get this message and a blank form.
Try changing the mode of the form to New - you can do this either by setting the Default mode of the form to FormMode.New or, if you're using a button or navigation from somewhere else to get here, add NewForm(FormName) to the expression to put the form into New mode.
If you just want to test, put a button on the screen and set it's OnSelect: property to
NewForm(FormName)
where FormName is the name of your form, and hopefully you should see what I mean.
Hope this helps,
RT