Form Rule to require file attachment?

When I test this in my app it does work but it is similar to a date field(and probably others) in that once the user interacts with it they must click out of it into another field for the form to update and trigger the rule.

The rule I tried was to require the attachment when the field is blank or empty. If I click "choose file" and pick a file and then do nothing else the field remains required. Once I have selected the file I must then click into another field, now the form rule triggers and it is no longer required.

Is that what was causing you an issue or was it something else?