The OP is using an Android TV, as stated, and Google Casting works in pretty much the same manner as with a separate Chromecast Dongle with the exception being you can set the TV up to connect via the TV rather than using the Google Cast App. I assume the TV has been setup and can see internet content, eg YouTube, via the TV interface at this point?

As Dunnersfella mentioned, the issue is likely with settings on the Vodafone router, I recall a similar issue occurring with an older ADSL/VDSL Vodafone supplied router a few years ago. Here's a link to some options to check off, I think there was IGMP or Multicast issues I had to resolve. This was with the Chromecast dongle, but essentially, it mean't the devices weren't talking to each other. Sorry I can't remember the exact method to resolution I found at the time.