Can't cast to Chromecast from Jellyfin via browser

[Paced5466]

I have Jellyfin server installed on Pop_OS and when I try to cast from my Jellyfin server media, using the Cast button, to my Chromecast I get the following error:

Code:

Your Google Cast receiver is unable to contact the Jellyfin server.

• Version: 10.8.10v
  
• Operating System: Linux (Pop_OS)
  
• Architecture: X64
  

If it matters, I also Emby set-up the same way and casting works fine.

I believe I may have an idea of what the problem may be. I have ZeroTier installed and from looking in the logs it looks like Jellyfin may be communicating with my Chromecast via ZT - which Chromecast is not connected to. Does that make sense?

I was going to attach the logs but they expose my ZT IP address.

thanks in advance for any help.