This is the limitation forced by Mozilla that only a hand picked add-ons can be listed for installation. Hopefully this limitation will be lifted, until then there is no other solution, just don't update the browser.

Please try new version 0.9.6. most of the issues should be gone now. And review the stars you've given :)

Is it similar to this issue?, i'm working to fix it. https://github.com/salarcode/SmartProxy/issues/121

Can you please post your request in here to keep track of it?
https://github.com/salarcode/SmartProxy/issues