Hidden form is not populating even though Autofill is set and default values are assigned.
One reason for this behavior is because the hidden form field is set to required. This is not supported for hidden fields and can only happen if the field is set to required before the field type is set to hidden. To fix this, we need to change the field type to something else, uncheck the required box, and set it back to hidden. Then approve the form and landing page and you should be good to go.