Please try : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

if that fixes the issue then it is possible Profile and or Extensions. Since do not have send info to Mozilla on I can not see your Extensions or if you should Update your Video Card Drivers as is a must to do.

Please let us know if this solved your issue or if need further assistance.

Do you see the Shockwave Flash plugin listed on the about:plugins and as enabled under the Plugins tab on the about:addons page? "3-bar" menu button or Tools -> Add-ons -> Extensions

You can find a Lego block icon at the left end of the location bar indicating that the web page uses a plugin (Flash) that Firefox might block. You can click this Lego block icon to allow or block this plugin.

• https://support.mozilla.org/en-US/kb/why-do-i-have-click-activate-plugins