In chrome on my desktop, when I leave fields blank, and submit the page, I will indeed get the "please fill out this field" text popup. When I view and try to do the same thing on an iphone, the validation is not firing, and the empty form gets submitted, and I receive the "success" message. I expect to see the same "please fill out this field" popup on the iphone, but I do not.
I'm not sure what needs to be changed to insure that the form is validated on any device. I've verified that the "Required" checkbox is checked on all form elements in the settings for each. Can't seem to get this to work.