I don’t know whether this is a problem with Microsoft office, firefox or my machine, I have already contacted apple support, and they said that it was not my machine. When I contacted Microsoft support, after describing the problem they ended the chat without saying anything. So this is what happened: I was at school. I tried to access my outlook email in firefox. I got an untrusted connection page. On the school wifi, since it restricts certain websites, you have to have a certificate installed in order to access secure (ones with lock icon) websites, I think so that the restrictor thing can see what webpage you are accessing. If it can’t read what you are accessing, it doesn’t let you access the page and you either get an access denied page, or on firefox a “this connection is untrusted” page. Earlier in the year I installed the certificate. for Firefox, I could click on a link that they gave us and it installed itself. for Chrome, I downloaded the certificate and imported it into my keychain. So when I got the connection untrusted page on firefox when trying to access a site that isn’t blocked, my school email, which is outlook/office365, since I had heard rumors about an updated version of the certificate, and having to install the new one, I decided to try reinstalling the certificate in firefox. So I used the wifi hotspot on my phone to go to my school email, the page that I couldn’t access before, I went to the school Sharepoint site for tech stuff, and clicked on the link to download the certificate. It said it was already installed. But it didn’t look like it was working on the school wifi, because I still couldn’t use the wifi to access outlook. So I tried to uninstall the certificate. since it said it was a certificate authority, I went into firefox advanced settings > certificates > certificate authorities and deleted the certificate called Bloxx. I might have forgotten a test here that I tried, but not anything else that I deleted. I found that it still wasn’t working. now I couldn’t access outlook at all. I tried uninstalling and reinstalling firefox. But the certificate I had deleted wasn’t there. I looked in my keychain, and I saw that there was no certificate called Bloxx in my system roots, but the other certificates I had seen in the firefox settings were there. When I got home, using time machine I backed up my computer so that anything I did from there on could be recovered. I hadn’t had any system backups before that. I saw on apple forums that I should try to reinstall the OS. I reinstalled OS X El Capitan. I can see the certificate I deleted is now there in firefox, but I am on the wifi at home which is not restricted at all, and I cannot access the office365, outlook, or any websites relating to that, even the products.office.com site. It says the connection is untrusted. However, on chrome, everything works.