Please make sure that port 80 is allowed for reverse connection on your remote session in either program, as well as make sure that the firewall allows this port to run as well. Outgoing is by default on, but not reverse.

One way to check is to see if this is also true with a remote connection to that computer from another computer on the same network. Configure firewalls so that Firefox can access the Internet

Connecting is not the issue. I can connect and everything else is visible. If I can the color scheme to 256 colors I can view Firefox.

just tested previous versions and the last version without this problem is 20.0.1