It connects, but then tries to redirect to another url that isn't accessible through the tunnel.
For instance, if you have Unraid's Lets Encrypt SSL certificate, any time you connect it will redirect to:
https://xxxxx.unraid.net
DDNS for that url will point to your LAN ip, something like 192.168.x.x, which isn't accessible when you choose "Remote access to server"
Because of this, you won't be able to access the webgui using "Remote access to server". Try "Remote access to LAN"