Downloaded FFv48 onto my computer and I did not import any data from other browsers. The first thing I do is go to FF Sync, and it tells me I'm not connected to the internet. I know I am because I downloaded FF from another browser. It's trying to go to about:accounts?action=signin&entrypoint=menupanel. I go to Dev > Network and I reload and get the HTTP headers. So it's doing a GET request to https://accounts.firefox.com/signin?service=sync&context=fx_desktop_v3&entrypoint=menupanel. The error that comes up is : An error occurred: accounts.firefox.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 It does not give me the option to add an exception, so I tried to do it manually by going to Preferences > Advanced > View Certificates. But that did not help and now I'm stuck. Please help!