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I did check your last edited form and I am able to replicate the issue you are having. PayPal checkout page displays error message after the form is submitted.
Upon checking your form, I found that you have not configured your PayPal payment question correctly. Please check the screenshot below:
In the "PayPal Account" text box, you have to actually input your PayPal account email address. Please input the email address which you use to sign in to your PayPal account and that should solve your problem.
Do get back to us if you have any questions.