I get an Incomplete Values after submitting the form

I just completed my form and tried to test it, and I filled out all required questions and went to submit and received an error that a required question was not filled out, but it wasn't the typical note at the bottom of the form, it was a separate pop up; photo attached. 

It's because of the Google re-Captcha widget that is set as required as well as the Preview Before Submit widget. You do not need to make these widgets as required in the form. The Google re-Captcha is always required and no need to set it as required from its properties. I've fixed it for you.

Thank you!