I recently deleted an old version of Firefox to get Firefox Quantum. Firefox Quantum wasn't connecting to any site, so I deleted everything: all app data (roaming and local), all registry entries, every little bit of Mozilla data I could get my grimy hands on. Then, I ran the actual uninstall file. I went to Mozilla again and downloaded the new browser. But still: every site, even Mozilla itself, had this error:
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.
No exceptions work, all my firewalls are down in that category, antiviruses are letting it through, I've rebooted, I've checked for SSL, I've searched and searched, I've changed all 4 settings that supposedly help in about:config, and I'm at a loss. All my other browsers (Opera, Chrome, Edge, and Internet Explorer) work! I've trouble shooted, with no problem, I'm on my own Wi-Fi with no injection and no website blocker! I have no malware, and I'm honestly so confused. PLEASE HELP ME BEFORE I LOSE MY MIND!\
I'm running avast antivirus, not blocking websites with invalid certificates, on Windows 10 Pro, version 1709, and OS build 16299.98. Smartscreen and Windows Defender are not blocking any of this, and I'm unsure about Windows Firewall.