UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3343.0 Safari/537.36

Steps to reproduce the problem:
1. Go to fepblue.org (I saw this with some other site recently also) 
2. note Privacy Error with "ERR_CERT_AUTHORITY_INVALID"
3. Click on red "Not Secure" in URL bar, and click "Certificates"
4. Examine certificate and CA certificates and note that all are "valid"

What is the expected behavior?
Browser should see that cert chain is valid and navigate to expected page.

What went wrong?
Browser weirdly says that the cert authority is invalid, but browser's own dialog boxes indicate that the cert chain is all valid.

Did this work before? Yes 2 days ago?

Chrome version: 66.0.3343.0  Channel: canary
OS Version: OS X 10.13.2
Flash Version:
 

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