Board Thread:Technical Help/@comment-3983273-20170215003411/@comment-4018164-20170216184730

Try to change the settings to stop it from blocking SWF files (possibly considered a 3rd-party extension), or try to temporarily disable uBO to see if this problem only occurs when it is enabled.

If none of these help, check out this superuser reply to a similar question. If nothing works, try uninstalling adobe flash player and installing it again.