Firefox 24.6.0 is far past being supported by Mozilla - July 2014 support ended for ESR 24. People shouldn't be using it in 2017.

I don't read that language. Might be helpful if you provided an English translation of what that installation message says. Or maybe provide a hyperlink to that pl Addons page. Can't copy & paste from an image, an I'll be damned if I t'ype it out and then run text though Google Translate to see what is says.

Check the Version Information at the bottom of that Addons page to see which versions of Firefox it is compatible with.

Hi. link to the same public addon https://addons.mozilla.org/pl/firefox/addon/jde-copy it is not accepted yet. I need install my private addon. Why FF stop installation and return failed installation process when private addon is accepted? I try in 31.0 ESR and FF return the same message (screens in attachment). When I install the same addon in FF (heighter than 50 not esr version) the addon works ok

Older versions of Firefox actually can't recognize webextensions as proper addons. Your extension is compatible with newest Firefox only, despite the compatibility info claims otherwise.

My private addon is compatible with older version (screen 1 in previous post). And it dosn't work. How to speed up the acceptance process ?