Kaspersky Protection 4.6.2.23.1 (light_plugin_D772DC8D6FAF43A29B25C4EBAA5AD1DE@kaspersky.com)

is shown as online.

Check Kaspersky for updates. And talk to their support.

Mozilla disabled Kaspersky. I've paid for that support. Mozilla and Kaspersky need to work this out, not me.

This will disable add-on signature enforcement; Enter about:config into your Firefox address bar Click the I'll be careful button Find xpinstall.signatures.required in the list Right click the preference Select Toggle until the value is false https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox

https://wiki.mozilla.org/Firefox/AddOns/Status/Updates#Exec_Summary “Currently targeting Signing with no pref to turn off in Firefox 47”

Separate Issue; Your System Details shows;

Installed Plug-ins

Adobe PDF Plug-In For Firefox and Netscape 15.10.20056 Adobe PDF Plug-In For Firefox and Netscape 11.0.14
Having more than one version of a program may cause issues. You must remove the older programs. Then get the current full installer.

Adobe PDF Plug-In For Firefox and Netscape: Adobe Reader Version 2015.009.20069 Note: McAfee Security is offered in the download.