The issue is NOT that 80 & 443 are being blocked.
The REAL issue is that traffic on those ports is not reaching the server.
What you need to do is setup Port Forwarding on your Router to forward both ports 80 & 443 to the server.
Note: Don't let the UPNP Setup fool you. I've never seen this work on any model of router that I've used.
The BEST way to get your Anywhere Access to work is to setup the Port Forwarding for 80 & 443 on your router BEFORE running the setup wizard in Essentials.
I have used the above method to setup Anywhere Access for both Server 2012 Essentials AND Server 2016 Essentials.