firefox addons: "could not be verified" when update exists

[^rooker]

I'm running good-old Xubuntu 12.04 (64bit).
I know it's old, but I'm experiencing a very strange behavior and this is a production machine which cannot easily be updated.
Anyways, I'd be very interested in finding out what causes this issue:

I've disabled all automatic updates for FF and addons.
Yet without any warning, addons are disabled displaying the following message:

"XXX could not be verified for use in Firefox and has been disabled"

This is bad, because it requires to update the Addon to the most recent version in order to use it again.
I require the addons not to change at all, in order to guarantee consistent behavior of this machine.
I've selected "Reset all addons to update manually", but this still happens :(

Any ideas where I could check why the addons are checked for updates?

Thank you very much in advance :)

[^rooker (rooker)]

Forgot: Firefox version v45.0
;)

[Paul White (paulw2u)]

^rooker,

Thank you for taking the time to report this bug and helping to make Ubuntu better. We are sorry that we do not always have the capacity to look at all reported bugs in a timely manner. You reported this bug some time ago and there have been many changes in Ubuntu since that time. Your problem may have been fixed with some of the updates.

It would help us a lot if you could test on a currently supported Ubuntu version. When you test it and it is still an issue, kindly upload the updated logs by running only once in a terminal:

apport-collect 1675939

and add any additional information that you think relevant. Alternatively, please confirm that this is no longer a problem and that we can close the report. If we do not hear from you this bug report will close in approximately 60 days time.

Thank you again for helping make Ubuntu better.

Paul White
[Ubuntu Bug Squad]

[Launchpad Janitor (janitor)]

[Expired for firefox (Ubuntu) because there has been no activity for 60 days.]