Same thing is happening for me in Chrome. It works in Edge. I believe Chrome made some sort of security change in a recent update. I am betting that Channels needs to push an update, or perhaps there’s some kind of workaround.
EDIT: It could be this, from Google: “Chrome no longer trusting certain Symantec certificates
As previously announced, Chrome 65 will not trust certificates issued from Symantec’s Legacy PKI after December 1st, 2017, and will result in interstitials. This will only affect site operators who explicitly opted-out of the transition from Symantec’s Legacy PKI to DigiCert’s new PKI.”