Can't edit custom form

I have installed Crono form version 4 and i have this message erroe
"You form type is "Custom" and so you can NOT add/edit the form fields (code) in the wizard, any fields you add here now will not be saved"
Why?

image errore

You must have changed it under the form edit screen, please click your form name in the forms manager and change the form type under the "Code" tab!

Regards,
Max