I have windows 7 and firefox 63.0.1 and cannot get on google.com because of a security issue. The error is as follows: www.google.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER I uninstall firefox and resinstall and it works fine for a short period of time. Then without warning, google no longer works and I get the security issue. I have uninstalled and reinstalled 4 times now and it is still doing the same thing. Works for a while and then not. I also tried using version 62 of firefox but that also exhibited the same issue. I researched this issues and there are all sorts of attempted fixes that supposedly get rid of this issue which I have attempted to no avail. Will someone please help me understand how to fix this issue. I use google and gmail all the time and this is becoming a real issue. Your help is much appreciated.