https://support.mozilla.org/en-US/kb/troubleshoot-issues-with-plugins-fix-problems https://support.mozilla.org/en-US/kb/warning-unresponsive-plugin ---------------- Remove Firefox's plugin registry file Sometimes the '''pluginreg.dat''' file becomes corrupted. You can remove it and have Firefox re-scan for plugins. As a side effect, any plugins you have disabled on the Add-ons page probably will be re-enabled, so you'll need to go back to that page one more time. '''Close Firefox. ''' Open your file browser to this hidden location: * '''Mac: ''' *~/Library/Application Support/Firefox/Profiles * '''Linux: ''' *~/.mozilla/firefox/Profiles * '''Windows: ''' %AppData%\Mozilla\Firefox\Profiles * *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles Search for the above file. Then rename or delete them. Restart Firefox.