AddBlock Plus is NOT working! Some others such as Ghostery aren't working either. When I click the Icon, nothing happens. How do I fix this problem?
Check with their respected Addon developer for issues with their addons.
They may need updating. Check in Add-ons and Themes (ctl+shft+a).
They have ALL been updated and still are not working. They were working a few weeks ago but as best I can tell, seem to have stopped working after the last Firefox update.
If you use Adblock Plus then you can consider uBlock Origin as a replacement to see if that works better (lower memory footprint).
As mysterious as to why those addons stopped working, they have mysteriously started working again! i hope this continues to be the case!
Sometimes a restart alone achieves that.