If http works and https does not work, the problem is probably with ca-certificates.
For some reason I have the ca-certificates from piCore-9.x, which are in /usr/local/etc/ssl, but the ca-certificates in piCore-11.x are in /etc/ssl and epiphany is probably not looking there.
You could try this command: $ sudo ln -s /etc/ssl /usr/local/etc
..and then restart epiphany and see if things work as expected