Out of the blue, I can't connect to any websites even though I'm connected to my WIFI network. When I open Firefox, I get an error just below the Bookmarks bar that says "You must log in to this network before you can access the Internet." When I click '''Open Network Login Page''' it sends me to https://myattwg.att.com/UverseAccount.html but I get a 404 Not Found error. I get '''MOZILLA_PKIX_ERROR_MITM_DETECTED''' when I visit any website using the computer that's directly having problems. I get the error '''SEC_ERROR_UNKNOWN_ISSUER''' when using another computer that's connected to the WIFI network. I've gone into about:config and changed '''security.enterprise_roots.enabled''' to '''true''' but that still doesn't work. I've tried to turn on/off Windows Firewall, but nothing either. I get similar errors with IE & Chrome. This isn't my computer I'm trying to fix the issue for (older family member), but I remember this computer having all sorts of antivirus programs installed like Avast, BitDefender, etc. I've read that those can cause problems with stuff like HTTPS Scanning but I had removed all antivirus programs a while ago and the internet was still working just fine. Any ideas? Below is the error I get in case you want to decode the certificate. Peer’s Certificate issuer is not recognized. HTTP Strict Transport Security: true HTTP Public Key Pinning: false Certificate chain: -----BEGIN CERTIFICATE----- MIICXzCCAcigAwIBAgICA/wwDQYJKoZIhvcNAQEFBQAwbjELMAkGA1UEBhYCVVMx DjAMBgNVBAoWBTJXaXJlMRcwFQYDVQQLFg5HYXRld2F5IERldmljZTEVMBMGA1UE BRYMOTkxNzFOMDYwMjc1MR8wHQYDVQQDFhZHYXRld2F5IEF1dGhlbnRpY2F0aW9u MB4XDTIwMDYwNzIyNTk0NVoXDTM1MDcwNDIyNTk0NVowTTELMAkGA1UEBhYCVVMx DjAMBgNVBAoWBTJXaXJlMRcwFQYDVQQLFg5HYXRld2F5IERldmljZTEVMBMGA1UE AxYMYXR0bG9jYWwubmV0MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDk9+CX 7aUUBKGFjq0UbSpo3ke80uGhj71TeTakJPGjVX2jwcx+2occV1e8tKLgqKl2/Kf0 Ms/ZKD8EpguvMLHme6t+XOWks+EVbdZCawE7TVxKLuzj7yBv7zh+01P1lxr8ND4f pnFQqGfamgS87oqhbQXCIduvaUo+J6D94YbrYwIDAQABoy0wKzAJBgNVHRMEAjAA MAsGA1UdDwQEAwIFoDARBglghkgBhvhCAQEEBAMCBkAwDQYJKoZIhvcNAQEFBQAD gYEAgISkGGqoyI8AbCPeb4oRiVm1n/Fq6piOEmzBj8egI3nCCZ7IKkHNMYXa0s9E KuAF8SiXqfBuWlGEwwbdg0cP5RZRuqmuNiQxVtVvjlOlYX2htIYP1FUdQrp7XXtp FG0333n32eJe5j8XGKPi/8qA5CWjPaRjvhZarqyEFN5VfNU= -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- MIICiDCCAfGgAwIBAgIBATANBgkqhkiG9w0BAQUFADBuMQswCQYDVQQGFgJVUzEO MAwGA1UEChYFMldpcmUxFzAVBgNVBAsWDkdhdGV3YXkgRGV2aWNlMRUwEwYDVQQF Fgw5OTE3MU4wNjAyNzUxHzAdBgNVBAMWFkdhdGV3YXkgQXV0aGVudGljYXRpb24w HhcNMjAwNTA4MjI1OTQ1WhcNNDAwNzAyMjI1OTQ1WjBuMQswCQYDVQQGFgJVUzEO MAwGA1UEChYFMldpcmUxFzAVBgNVBAsWDkdhdGV3YXkgRGV2aWNlMRUwEwYDVQQF Fgw5OTE3MU4wNjAyNzUxHzAdBgNVBAMWFkdhdGV3YXkgQXV0aGVudGljYXRpb24w gZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBALRg97VidcSZoXYBbG9AYa41gXkt uTILyX5hhdz+cxwPuKFxM3Nws7h3c08PPUjrE2TpsVgfrB/25XpwmgLSTfftAEv5 eC60Za05Eu86rRv+OU4UN2Rvokl4GhB0pxOjOVPzVcpXWTFdJlNiYhwYLehBKLNO 2xwlzI/DJjdXhzxHAgMBAAGjNjA0MA8GA1UdEwEB/wQFMAMBAf8wDgYDVR0PAQH/ BAQDAgEGMBEGCWCGSAGG+EIBAQQEAwICBDANBgkqhkiG9w0BAQUFAAOBgQBggJ8C jetJxINhlk37EVDHweQa/JwfKq1x2gCpacs8YtIxLwsfhT5nQlkujJ7VZpd3CK7H VdTEjidGgLiYYi8Q7hSyUbNt7dtH0WXMBtjLu/Na4VGUpojJf+jLaC6pnCrGUj3F b/K+M8Y/POcgqOVfzTnHsZQWnnkAQmxyFI0uzA== -----END CERTIFICATE-----