Web Compatibility Support • cosmote.gr - pop-up prompt does not appear

Hello everyone,

This occurs in a logged in section of the website, so for now I can only provide the main page link and screenshots.

https://my.cosmote.gr/selfcare/jsp/dashboard.jsp (specific login page)
https://www.cosmote.gr/hub/ (general website)

In the account details section, there's a button. Pressing it should darken the rest of the page and have a new, small information window/prompt appear. It looks like this:
On Pale Moon, clicking on that button does nothing. No changes, messages or pop-ups. Below, a screenshot of the Error Console. I think the top, highlighted entry is the one related with the pressing of this button but not entirely sure. It does not appear immediately after pressing it.
Also tested on current, clean PM Portable.

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