Hosted Payment page only loads in Firefox

Our hosted payment page has been working flawlessly up until about 10 days ago. Now it only seems to work in FireFox browser and not in Chrome or Edge anymore. When the user clicks to proceed to secure payment page (https://www3.moneris.com/HPPDP/index.php), its just a blank page and nothing loads. So strange that it still works in Firefox.

Any idea how to fix this?

Thanks in advance for any help.