Can people submit more than one time on my form?

Hello,

I had a client try to submit a 2nd time on the form but could not. Is there a way to change it to allow a certain number of submissions? or does it clear after a day so they can submit again? Form in question is here http://www.thetravelingsoldiers.com/membership-sign-up.html she had issues with pay pal and got it straight but it wouldnt let her submit the form again, said she already submitted... 

Thanks

You've enabled unique submissions in your form and this is why it cannot be submitted again by the same person.

You can disable this feature temporarily to allow your user to submit the form again and then enable it again.

If you need further assistance, please let us know.
Thanks.