Casting from jellyfin app over remote connection?

Hi, I recently gave my friend connection to my server and he was trying to cast a movie to his TV from his phone however it wasn't working. I have my jellyfin server running on my unraid machine on my lan and the public ip address is on a Linux VPS with iptables to point back to my lan. Any one know what I need to do to get it working remotely? What is also weird is that he was seeing my TV under cast when he was trying to connect.