Pop-up doesn't close

Hi,
I love this plugin! The only issue I’m having is that the I can’t close the pop-up that appears when you click on the ‘Schedule an Appointment’ button. The only way to close the pop-up is to refresh the page. I hope someone can help me fix this! Thank you in advance!
Paola

https://ww.wp.xz.cn/plugins/appointment-calendar/