Getting an error message that I can only submit my forms once and multiple submissions is disabled

Why after having made all the adaptions  to mine form, I still receive when clicking on "testing my form" the following message: "Sorry just one subscription is allowed, More subscriptions are disabled for this form". I don't understand how I could get rid of this message. Which modification must I do? I try to find something in yours tutorials but didn't see something about this. Could you help me?

The message that appears every time you try to submit your form is caused by the option shown in the screenshot below. 

To learn more about that option, please refer to this guide — How-to-Set-Unique-Submissions-on-a-Form

If you have other questions or concerns, please feel free to contact us again anytime.