Hello again
I have novell moonlight which I installed a while ago so I'm not sure it's the same thing you have but it works on the silverlight websites I've tried, in your home directory is a hidden file .mozilla dig right down to the install.rdf i.e .mozilla/firefox/63ixi0xc.default/extensions/moonlight@novell.com/install.rdf
the "63ixi0xc.default" will most probably be different on your system.
open the install.rdf and look for this line
Code:
<em:maxversion>9.0.*</em:maxversion>
and change it to the version of firefox you have, you can do this with most addons btw, I haven't tried it but you could probably replace the version number with * and it'll never need updating.
You may then need to restart firefox
Hope this helps