Hi,
Judging by the source code, the problem occurs because when you click Print, the PrettyPhoto script starts to work. It is a part of your Avada theme. This script is responsible for opening an image in lightbox, and since an image is used for the button, the script tries to open the image in lightbox instead of opening a page to print.
Here is the link to the print version of your site-
https://www.lanka-school.com/%E0%AE%AA%E0%AE%B0%E0%AE%BF%E0%AE%9A%E0%AF%8B%E0%AE%A4%E0%AE%A9%E0%AF%88%E0%AE%95%E0%AE%B3%E0%AF%81%E0%AE%95%E0%AF%8D%E0%AE%95%E0%AF%81-%E0%AE%AA%E0%AE%AF%E0%AE%A9%E0%AF%8D%E0%AE%AA%E0%AE%9F%E0%AF%81/?print=print. Please contact your theme’s developers with this problem.
Sincerely,
BestWebSoft Support Team
