The IP in shell.ps1 should be your own HTB-assigned IPv4 address. You can look up your IP addresses like so.
$ ifconfig tun0
inet x.x.x.x
inet6 dead:beef:x::x
inet is your IPv4 address while inet6 is your IPv6 address.
After which, you should start your netcat listener like so.
$ sudo nc -lnvp 443