There are several statuses associated with Projects:
Draft - This is non-discoverable and non-public facing.
Private - This will be hidden from any type of search engine and will only be accessible to those who have the link.
Public - This is discoverable and should be used if open to public submissions.
Firstly, make sure the most recent version of the form is updated by heading to Projects > Form Builder and selecting Publish changes.
Next, change the status of a Project heading to the Visibility section and change from Draft to either Private or Public.
Once activated, this will become enabled and creators will now be able to submit material.