Your connection is not secure

Hi guys, my granddaughter has this popping up everywhere she try's to go outside of Firefox ! It will open FF and IE fine but if she try's to go to any other site this message pops up !! We were trying to open Google, like i said every site gives this message. We checked the clock & date, they are correct !! Now i am lost, any ideas of what to try would be appreciated very much ! She doesn't use her computer much so it may be awhile before i get back with an answer for you !!
Thanks

Your connection is not secure

The owner of Google has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate.


Forgot to mention that everything works fine in "Safe Mode with networking"

Thanks

what anti virus software are you using?

what windows operating system are you using?

and last what firefox version is installed and what addons have been added?

because things work in safe mode i'd be thinking the problem is most likely to do with the antivirus program your using, so a quick check is to start in normal mode and then stop your anti virus from running and see if you can then connect to https pages without getting that error message.

Had already tried all your advise before which did not work ! We fixed the problem by installing W10 !!

Thanks

Chuck