Submissions will not populate while using forms and an error is given on submit

Question:
How do I get submissions to populate while using Forms?

Product:
Wix Editor

What are you trying to achieve:
I am trying to use Forms, having created my custom form. I cannot submit any data, and there are no submissions being populated.

What have you already tried:
I was told that the form would work when the site was published, but this is not the case. I have also tried remaking the form, but I get the same error. I have also made sure that all fields are entered correctly.

Additional information:

Are you using the App or CMS Collection?