you need to check whether '''jdownloader''' is compatible with the Firefox version you are using. -> Tap ALT key or press F10 to show the Menu Bar -> go to Tools Menu -> Add-ons -> Extension section -> check the Status of '''jdownloader''' extension -> if '''an update''' is available for this add-on then install the update -> Restart Firefox and check again check the compatibility -> if it is '''GREYED with Exclamation mark''' then it is incompatible with Firefox Try using this extension to force compatibility. https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ Check and tell if its working.