If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, DuckDuckGo PE, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content. You can click shield icon for more detail and possibly disable the protection. You can check the Web Console for messages about blocked content.

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track

You can try these steps in case of issues with webpages:

You can reload webpage(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" for websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Data"

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or userChrome.css is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track

Thanks Cor-el. I tried disabling enhanced site protection, paused ghostery, disabled other extensions and set popup blocker setting off. Still no popups from the site in question. Any more suggestions anyone?

Does Firefox show the "popup blocked" icon in the address bar next to the lock? If not, there probably is some other reason the popup isn't appearing -- a reason other than the popup blocker such as a blocked or broken script.

Does this popup work: https://www.jeffersonscher.com/res/popup.html

Thx jscher2000, Firefox does not show the pop-up blocked icon as I had previously dismissed it. However I have tried your popup link and I get the text "A script in this page attempts to load a popup window after 1 second". No popup appears but this page opens in new tab: https://www.userchrome.org/.

Okay, if you got a new window/tab on my test page, turning off the popup blocker worked. I don't know why that isn't working on the sites you care about. Something else is going wrong....

Ok, thanks for your help. Mousing over the link I cannot get to work shows its trying to run a java script. This site and links works no dramas on MS edge.

Mousing over the link I cannot get to work shows its trying to run a java script. This site and links works no dramas on MS edge.

I guess you can't mention the specific site, or there's no public link? If you can, that might help speed up the diagnosis compared with check this, check that.

Unfortunately the issue happens on a private part of the site. The public facing part of the site is: https://www.nabers.gov.au/.

But that is prob no help.