signature canvas not working on popup

Hi..
Hope someone could help me here, I put a contact form on popup (as per other thread), all works well. But I need to have a signature canvas from contact form now. The signature canvas works well on the website body, but it doesn’t work on popup.

Please kindly see it here:

You can see the signature canvas works on the bottom of the page, then please try to click on “redeem” button, it will show a popup with contact form, same form as the one on the bottom of the page, but it doesn’t work there in popup..

Please kindly help..

Thank you,
Surya