From https://bugs.chromium.org/p/chromium/issues/detail?id=647910#c11:

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Original reporter:

Please enter a one-line summary:
DevTools' Security panel doesn't always show specific errors when overview marked "not secure"

What part of the browser is affected?
The Security panel in DevTools

Steps to reproduce the problem:
1. Have an expired client certificate
2. Load a webpage that requires this client certificate
3. Open the DevTools' Security panel

What is the expected behavior?
At least one warning or error message in the details to explain the overview label: "This page is not secure".
This panel really shines when user-friendly messages are displayed to help the less technical-oriented users.

What went wrong?
Although the overview displays a message "This page is not secure" (which is correct in this case), the details show no error. This creates confusion for the end user.

Did this work before?
  Not applicable or don't know  Yes - This is a regression  No - I think it never worked  

Any other comments?
Sometimes the actual TLS error is not even displayed in the main browser window, as shown by #646567.
Please see #647910 for more history on this issue.

[Screenshot from reporter attached.]

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Me: We can't really show much of the information in the security panel when a network error happens. I would probably probably suggest having the UI so something uninteresting and mostly blank. Fundamentally, clients are not in a position to know anything about the server's configuration or why something failed. (Notice how SSL Labs takes so long to give you a report. That's because it needs to do 10s if not 100s of connection attempts with different parameters to probe the server's (likely) preferences.)
 

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