Hi KamT, the problem usually is a "man in the middle" intercepting your browser. That can be innocent, like your security software, and not a hacker. Let's see if we can quickly get to the bottom of it.

For starters, on the error page, can you click the "Advanced" button and see what code is listed there? It has ALL_CAPS_WITH_UNDERLINES. Then check the following article to see whether it helps you sort it out. Please let us know if it doesn't and what code you're getting:

How to troubleshoot security error codes on secure websites

Thank you for sharing your add-ons list. Maybe coincidentally maybe not, you have an extension named Ad-Blocker 4.0.0. That has very mixed reviews on the Add-ons site, and is "not recommended" on an extension analysis site, so you could consider disabling it, along with any other non-essential extensions, to see whether that makes any difference for you.

You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove).

Any improvement?

SEC_ERROR_UNKNOWN_ISSUER

Sorry. First time.

I am trying to follow along

Do you use any of these security programs that intercept your web browsing: Avast, AVG, Bitdefender, ESET, or Kapsersky?

The article has steps to work around issues caused by those programs: How to troubleshoot security error codes on secure websites

Disabling Ad-Block did nothing. Are you suggesting I turn off my McAffee? And, then re-install it?

You can check if there is more detail available about the issuer of the certificate.

• click the "Advanced" button show more detail
• click the blue error text (SEC_ERROR_UNKNOWN_ISSUER) to show the certificate chain
• click "Copy text to clipboard" and paste the base64 certificate chain text in a reply

If clicking the blue error text doesn't provide the certificate chain then try these steps to inspect the certificate.

• open the Servers tab in the Certificate Manager
  • Options/Preferences -> Privacy & Security
    Certificates: View Certificates -> Servers: "Add Exception"
• paste the URL of the website (https://xxx.xxx) in it's Location field

Let Firefox retrieve the certificate -> "Get Certificate"

• click the "View" button and inspect the certificate

You can see detail like the issuer of the certificate and intermediate certificates in the Details tab.

https://www.yahoo.com/

Peer’s Certificate issuer is not recognized.

HTTP Strict Transport Security: true HTTP Public Key Pinning: false

Certificate chain:

MIIFhjCCBG6gAwIBAgIRAJUaDc7aADgFCJY2nd9SZ3EwDQYJKoZIhvcNAQELBQAw HjELMAkGA1UEBhMCRU4xDzANBgNVBAMMBlN0b3BBZDAeFw0xOTAyMDEwMDAwMDBa Fw0xOTA3MzExMjAwMDBaMGMxCzAJBgNVBAYTAlVTMRMwEQYDVQQIEwpDYWxpZm9y bmlhMRIwEAYDVQQHEwlTdW5ueXZhbGUxETAPBgNVBAoTCE9hdGggSW5jMRgwFgYD VQQDDA8qLnd3dy55YWhvby5jb20wgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGB AKLZTPtRmoH1moZ//Pja+bgEYqrc6SIBOdgsKsbw5nLKNdxV6ypQ0by0mnfbvKEz lU3HCWsU9EUyEIDCJ0hXlQqGcukni+/+8Zc4mqbebdDsy8HnLY7iws3XHC5oxUGZ pBUr67mk8zh9gXXt0ifXN7GXySGMRruAL3nMUrpIOhTlAgMBAAGjggL8MIIC+DCC AscGA1UdEQSCAr4wggK6gg8qLnd3dy55YWhvby5jb22CEGFkZC5teS55YWhvby5j b22CDiouYW1wLnlpbWcuY29tggxhdS55YWhvby5jb22CDGJlLnlhaG9vLmNvbYIM YnIueWFob28uY29tgg9jYS5teS55YWhvby5jb22CE2NhLnJvZ2Vycy55YWhvby5j b22CDGNhLnlhaG9vLmNvbYIQZGRsLmZwLnlhaG9vLmNvbYIMZGUueWFob28uY29t ghRlbi1tYWt0b29iLnlhaG9vLmNvbYIRZXNwYW5vbC55YWhvby5jb22CDGVzLnlh aG9vLmNvbYIPZnItYmUueWFob28uY29tghZmci1jYS5yb2dlcnMueWFob28uY29t ghJmcm9udGllci55YWhvby5jb22CDGZyLnlhaG9vLmNvbYIMZ3IueWFob28uY29t ggxoay55YWhvby5jb22CDmhzcmQueWFob28uY29tghdpZGVhbmV0c2V0dGVyLnlh aG9vLmNvbYIMaWQueWFob28uY29tggxpZS55YWhvby5jb22CDGluLnlhaG9vLmNv bYIMaXQueWFob28uY29tghFtYWt0b29iLnlhaG9vLmNvbYISbWFsYXlzaWEueWFo b28uY29tggxtYnAueWltZy5jb22CDG15LnlhaG9vLmNvbYIMbnoueWFob28uY29t ggxwaC55YWhvby5jb22CDHFjLnlhaG9vLmNvbYIMcm8ueWFob28uY29tggxzZS55 YWhvby5jb22CDHNnLnlhaG9vLmNvbYIMdHcueWFob28uY29tggx1ay55YWhvby5j b22CDHVzLnlhaG9vLmNvbYIRdmVyaXpvbi55YWhvby5jb22CDHZuLnlhaG9vLmNv bYINd3d3LnlhaG9vLmNvbYIJeWFob28uY29tggx6YS55YWhvby5jb20wDAYDVR0T AQH/BAIwADAdBgNVHSUEFjAUBggrBgEFBQcDAQYIKwYBBQUHAwIwDQYJKoZIhvcN AQELBQADggEBAJnYHRhuqTjif5jwdBjPX3aNFpw4LGpnimHoUOmZ7WhggtietgCk 8+yyAGYCI7q4KIkFe7cHZmGlhdxojsgDYbilOzodtB1O1FIfz9fg/tGDcE0CsEJb gEzYqq7abaLb7owXv8D9DbmIOkZkYVMxA/Ez17APbjP2xqOHrTXFPB/7cN3Ut3Vp MFjum3lXpyY7JKjnPmCnYgTv6C9B4BjZRiu5W0dPA3tZk6zciN/GdrjFFInoe2jg Fd3SBx/jcVSBEOjQLaHc8c4AK0m5PVGJqAZpL/6qsM3v1S1scy6QoYD3r3NdCMwi hQ7cLmEcoYy4ERfEFMeQvZ9f8WR61mHcmTo=

The issuer of the certificate is StopAd.

• Issuer: C=EN, CN=StopAd

Are you using this software?

• https://stopad.io/
• https://stopad.io/help/windows/connection-is-not-secure

Thank you!! Gosh, thank you all for taking time out of your day to help. I am grateful.