Casting from YouTube does not work for me.
Testing on a brand new FVP-4000T (I know I should have listened to you guys) and the latest firmware, casting from 5 devices:
Kindle Fire 2015 tablet running nexus firmware - nope - not surprised as the apps are well out of date...
Huawei phone - nope - not too surprised as they only support casting to other Huawei devices...
Samsung Galaxy S5 - nope - I would have expected this to work as it's fully up to date...
Windows 10 laptop with Chrome - nope - looking like the Humax is broke...
Chromebook - you can't get more Google than that - nope..!
In all cases, the Humax goes to a blank screen followed by the YouTube logo - then the normal YouTube homepage for my account, but the selected content does not play.
The Humax remote and live TV can all find the device and work properly so I'm happy with the network, but the Humax Cast app cannot find the device.
All devices can Cast to my Roku.
I wonder if it's worth trying the older firmware...