If you’re receiving the error ERR_CERT_COMMON_NAME_INVALID when trying to install extensions, and you’re on Verizon FIOS internet, try this fix:
Log into your Verizon app
Internet → under Parental controls → Home Network Protection → Turn Off
I struggled with this issue for months with none of the suggested fixes working until I finally discovered through Fiddler captures that it was being blocked by McAfee, which I don’t have installed on my laptop.
Hope this helps someone.