hi, first please make sure that the date, time & timezone are set correctly on your system. if this doesn't solve the issue (or it is already set properly), a solution depends on the individual circumstances:

• what is the error code shown when you click on advanced on that error page?
• please also give us more information about the error by clicking on the error code, copying the text to the clipboard and then pasting it here into a reply in the forum like shown in the screenshot.

thank you!

Thank you so much, Philipp, i work with computers, so my time, etc... are all correct.

This happened after the last update. It happened once before right after an update, i had to manually find all my homepage sites again, put the search bar back, etc...

Not even Google works. And not even Mozilla as you will see here since you asked me what happens after i click on "advanced"...I appreciate your help, by the way, am just really frustrated as i work with websites. www.mozilla.org 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

can you provide the second part of information i've asked for too (like the screenshot is showing)? hopefully this will give clues as to what's wrong...

Thank you so very much, Philipp, unfortunately your screen shot didn't show in my email, so i used another way of getting here. Here are two of my screenshots:

yes, on the error page please click on advanced, then on the blue SEC_ERROR_UNKNOWN_ISSUER error code, then on the button to copy the text to the clipboard and then paste it into a reply here on the forum (in text form, not in a screenshot - because transcribing that would be quite tedious)

I apologize, didn't get that..:) Here it is: https://www.mozilla.org/privacy/firefox/

Peer’s Certificate issuer is not recognized.

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

Certificate chain:

MIIEUzCCAzugAwIBAgICB/4wDQYJKoZIhvcNAQELBQAwaDELMAkGA1UEBhMCQ1ox DzANBgNVBAgMBlByYWd1ZTEOMAwGA1UECgwFQVZBU1QxHTAbBgNVBAsMFFNvZnR3 YXJlIERldmVsb3BtZW50MRkwFwYDVQQDDBBBdmFzdCB0cnVzdGVkIENBMB4XDTE2 MTEwOTAwMDAwMFoXDTE4MTExNDEyMDAwMFowggECMR0wGwYDVQQPDBRQcml2YXRl IE9yZ2FuaXphdGlvbjETMBEGCysGAQQBgjc8AgEDEwJVUzEbMBkGCysGAQQBgjc8 AgECEwpDYWxpZm9ybmlhMREwDwYDVQQFEwhDMjc1OTIwODEeMBwGA1UECRMVNjUw IENhc3RybyBTdCBTdGUgMzAwMQ4wDAYDVQQREwU5NDA0MTELMAkGA1UEBhMCVVMx EzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDU1vdW50YWluIFZpZXcxHDAa BgNVBAoTE01vemlsbGEgQ29ycG9yYXRpb24xFDASBgNVBAMTC21vemlsbGEub3Jn MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4AMj5J6O0tOpHkywQDM6 RmfVUrCXsHdGHZKLwSVsf+wqXeBWDPB+Hidyms7N7FVGIxgbbVrct9YZEv6AzT6v 4vOYvxKR7RVlScC7+Nspiyy/YQ6LQnwe/mWoMrYFZ0AG82ODBq0OEuctn4Gp7HFI fg8Fc9VYuajGV0Rl4oJ3phu8CtH+GTjYv+oCyVqASQdeVgB5y1PG3XXay+QPCLJa i3TJUO2TYODnDMan3YYwdlUXcZUItTxxmN3UqD1I5EViQJBPTAbYu0ziteEvDc4c FwWjr8Hz9WqQDoWlDDO4132o4KnoRCgIr7grID57BVOKX4PuZVYjfzrDMeJcFgGd wQIDAQABo2swaTAdBgNVHQ4EFgQUhwM7KOUntkXL7tPotJftOBX+J9YwHwYDVR0j BBgwFoAUPGKyiaAnORz4kt8/U6G1s8mrJYQwJwYDVR0RBCAwHoILbW96aWxsYS5v cmeCD3d3dy5tb3ppbGxhLm9yZzANBgkqhkiG9w0BAQsFAAOCAQEASRXxHJgsZts0 NJUqP7Dn3PPfpRBDdP6ZsAk1jOwSLJ/9W61Soae16m9cueph18b5xB+csyngSaf3 g2kFeFkRvkg29veYtVkam9pLuYHbffpVDvcO4S6nuZ0QNlZJpltrIVWDZSgG6rvY qC+dwnIGvNr1VHhaJsbXYSkseZJ8aAcgkc2tmXx00xCp58qaaRXLaHkl7V/S6VDi xrWR7D4n0tOBtyu8Csi85rLTiifCNCpLY5XG9lvXL4ZB2n8m5zQpliyOU4kMbGo8 Gqnr8b2Uj37FJLlc8Uk9q6Jun0/3xb/ivoCqDgx0boqfrknDEXgL/nusOYke8leY 6NltX31cYw==

thanks, unfortunately it's your avast security software meddling with secure connections in this case - please try the steps explained at https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER#w_avast

I will try to do that, even though i already tried some of that with Avast the first time, I will have to contact them.

It is just too bad that those things happen with updates though...and why remove the old ways of search bar and homepages....?

Anyway, thanks so much for all your help, Philipp. I do appreciate it and will follow up on it. Thanks for your prompt replies. Anita

One last thing, Philipp. I would like to apologize for blaming Mozilla for causing the problem since it was apparently Avast's problem

I would like to however help you with the fixing it as it seems that the solution you showed on Avast is a little outdated: My Avast Pro doesn't show "settings". And not how to disable HTTPS. I had to go to "preferences", under" Web Shield": unchecked "scan secure connections" and also unchecked"Scan secured connections from browsers only". Not sure if that puts me at risk, but it worked for now. All my sites show again. And I am contacting Avast. Thanks again, Anita