Hey there,
When 'required' attribute is added to input types 'select, date and file', it doesn't put a red border around the field in case that is not either selected or chosen while clicking on the submit button. If everything else is filled while not selecting the mandatory file, it doesn't do anything. This is an expected behaviour but it should let user know that one needs to choose a file to submit the form. See the attached screenshot for a reference.
