Melody: Can you perform outreach to determine
1) Are these only Windows users
2) Are they running Windows 7
3) Have they ensured their Windows is up to date?

If 1 & 2 are true, it's likely a duplicate of Issue 588789

This is a report that is tagged with Windows 10:

https://productforums.google.com/forum/#!topic/chrome/JwqtwATDAFI
(have followed up to confirm)

And and here's one from an Ubuntu user:
https://productforums.google.com/d/msg/chrome/O_QaFFi_rgY/1SXm2OTBBwAJ

Hi there,

its Windows 10, latest Update. 
Chrome see pic. Update shows not possible....

Think your Chain Cert is the problem. It is only SHA1 and only valid to 01.01.2017....

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Can you attach a chrome://net-internals log (see https://dev.chromium.org/for-testers/providing-network-details ) to Issue 588789? Thank you

Oh, and trying Chrome Canary - https://www.google.com/chrome/browser/canary.html - or Chrome 55 should resolve the issue.

I got in the same browser only a few tabs later,

these two pics. The Chain-Cert has changed....
I got one with end 01.01.2017. In a second tab i got one with 01.01.2018....
The 01.01.2017 is definitly SHA1....

Think that causes the problems. And the question, where did the different cert come from...

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I appreciate the help, but could you please comment on Issue 588789 with a chrome://net-internals log? That would be far more helpful than the screenshots :)

I am sorry. I have absolutely no experience with that. And i don`t know what i exactly should do. And what data all the logs contain... Still have to read the docs on that....

@bueroa...: Are there problems with the instructions @ https://sites.google.com/a/chromium.org/dev/for-testers/providing-network-details ?  If so, I'd be interested in improving the page.

ping bueroa@, please use the link in #10 for instructions on how to log your error.

I too had this problem with this weak SHA-1 certificate.This affected all services that are from google, like google, gmail and youtube. I uninstalled chrome serveral and also deleted the files related to chrome in the $appdata folders, just  to be sure everything was gone. Reinstalling it, didnt solve the issue. Also resetting the browser did not fix it. I opened up firefox and the certificate there was working just fine.

I download Chrome from the dutch server (chrome.google.com) I thought it might be possible that it has to do with this server. Therefore i decided to download chrome from another location. i went to ninite.com and installed chrome via their installer. (it grabs chrome from the US servers).

After installing Chrome that way, the problem was gone! Before all that i exported the certificate to my desktop, so i will add it here to be reviewed by google.

greetings, Mike

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Closing due to lack of response (specifically the net-internals log requested in c#10 & c#11).

I deleted my comment #13 because the problem seemed fixed, and then today it reappeared. However, my son did some research, and it's the Google Internet Authority G2 certificate that has a SHA-1 signature. It expires on Dec. 31, 2016, so until Jan. 1, 2017, I'm ignoring the error message. If it's still happening after that, I'll rerun a net-internals log.