Hey,
You changed the Truenas GUI ports, that's the problem. The Hexos button is pointing to the port 443 (https) or 80 (http) but nothing on the server is listening at that port thus the rejection.
You currently cannot change the destination ports of the truenas gui button in Hexos. To keep its functionality, you need to revert back to the ports 80/443. If you want to keep your custom ports, bookmark the page in your browser 🙂