Since updating to the latest version of Firefox, the LastPass addon is no longer installed despite the fact that it was there and functioning properly with the previous version. I'm not sure if the fault lies with the browser or the addon itself, so I'm firing at the issue with both barrels by posting a thread here and on LastPass's forums to figure out what went wrong. I have attempted to re-download the addon from Mozilla's addon repository, and from LastPass's website but despite having done so, the addon will not install and appear in Firefox.

There are no errors or anything immediately obvious that would explain what went wrong, it's just simply not there anymore.