Problem with button accessibility (due to security)
In my anonymous login, everything works fine. So I added associated entity to users (e.g. Cars - user can during registration add as many cars as he wants to). I set Access rule to Anonymous role. In the form, I have added dataGrid (source Association) and added 'New' button (+generate the script). There are no errors but the button New is not visible. if I change visibility to 'Ignore security' it does appear but does not work. I ran out of ideas where else could the security problem be.
Try looking at the entity access for entity cars.. anonymous users are probably not allowed to create a new car.