is there any error message or indication why it is failing when you try to directly install an extension from addons.mozilla.org for example?

I'm sorry, it appears that I have misspoke. Addons installed directly from Mozilla's site has no issues installing, but when I try to install one from a different site it doesn't work. When I try, the addon icon appears next to the address bar like something is about to happen, but then nothing.

I attached an image that shows what I'm referring to.

when you click on that icon, can you allow & jumpstart the installation of the addon (see screenshot)? firefox is set to block addons from 3rd-party sites per default.

Try to disable hardware acceleration.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes
• https://support.mozilla.org/kb/Unable+to+install+add-ons

Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

If the new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

The hardware acceleration advice fixed the issue! Thanks a bunch!

You're welcome