Prevent modal box from closing after using coupon code

Hi all.
My problem is that the modal is applied with the plugin “paypal payments” were I can add a voucher code. However, after typing the code I click on the coupon button, the page refreshes and closes the modal. I then have to open the modal agian in order to see the code is active.

How to let modal stay open efter typing the coupon code?

Kind regards

Mads

https://ww.wp.xz.cn/plugins/easy-modal/