How do you fix form fill issues?

I have someone trying to register on one of my forms and they are getting a message that says " Enter a valid email address" whenever they try to fill out one of the form fill sections on the form I created. I've never had this issue before, can you please advise?

I believe this is because you used the "Email" field in the "Quick Fields" section for those fields, that is why it shows the error message "Enter a valid e-mail address". OR you have set the validation as "E-mail".

Here's how I checked this. In your form builder, you can see that the "Validation" option is set to "E-mail":

In the properties of those fields you can see there's a "Confirmation Text Box" under "Options" tab which would indicate that this field type is an email field. Any inputs that is not a valid email address will prompt an error message.

You can either change the validation OR delete those fields and replace them with a generic "Text box" field under "Basic Fields". 

I hope that helps.