Mozilla Support reports that recently updated Internet security programs can cause connection issues. The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. Full-range color levels are now supported for video playback on many systems. Get the not-for-profit-backed browser on Windows, Mac or Linux. So, a full system scan can fix this problem as well. ***Post moved by the moderator to the appropriate forum category. To Access Safe Mode Do The Following: Step 1: Press the start button, click the power button, press and hold shift on your keyboard and choose the restart option. I have looked at my Norton AV logs and it does not mention anything around the time that I tried to run FF, nor does it mention any prevention of any program execution. Firefox did not connect When loading your domain in the FireFox browser, you're presented with 'Did Not Connect: Potential Security Issue'.