Firefox has a basic popup blocker anything beyond that is user installed Addons. It could be your security software has it's on adblocker causing this as well. So unless your using Firefox Private Mode Browser to verify there isn't a browser issue it sounds more like the security software caused.

You could try switching off Enhanced Tracking Protection. While on the website, press the shield icon at the far left of the address bar and use the button provided.

Does it still happen in Troubleshoot Mode?

If you use Private Browsing mode, try to switch to regular mode,

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history