It sounds as though the ad visuals are being blocked, but the function of the page to show it is not being blocked, so you just get a blank overlay. That's not helpful, since you can't see the close button that presumably is built-in to the ad.

You have quite a few add-ons, and sometimes an extension may be responsible for removing -- or adding -- ads on a page. Could you try this:

Disable ALL nonessential and/or unrecognized extensions. If you can live without it for 24 hours or you don't know what it does for you, if in doubt, disable:

orange Firefox button (or Tools menu) > Add-ons > Extensions category

Then restart Firefox using one of the links on a disabled extension and test again. Does it make any difference?

That worked, but I am not sure what I disable that made it work, so I guess I will see what doesn't work from the disabled apps.

Hi THSMTHS, as you revive the extensions you want to use over time, you may encounter the problem again. Then you'll know which one is the culprit.

In case it's simply a problem with an extension being out of date, you can try updating them using this menu:

orange Firefox button (or Tools menu) > Add-ons > "gear" icon > Check for Updates