We recently updated our ZNC server (don\'t think this matters) with a new certificate to include a Subject Alternative Name (SAN) DNS field. It works now in incognito but my
Restarting the browser gets rid of the "Active content with certificate errors".
Some people rarely restart their browsers though, would be good to know how to resolve this without a restart.
Update: A newer answer explains how to do this without a restart > https://stackoverflow.com/a/46390363/292408
This may be equivalent to the other methods but I found it while trying to avoid restarting my browser.
To clear this error without a restart:
Commenters have pointed out the following: