UKmatC

This doesn't work because there is no 'hard' source selected in your situation, but digital media instead. With the inclusion of all the streaming options in recent years, using 'current selected' really is more or less dead.
 
As others have mentioned, the room control driver(s) should be added for you. Dealer can do this -literally drop in the drivers (I would just ask to get this done for every room with audio or video in it)- and from there you can set everything from within composer HE

Best thing I did was getting the Room Control Drivers and deleting all Media Scenes. the Room Control Drive is 1000% better. 

Lots of ways to do this but Room Control Driver is definitely the easiest.  Media Scenes (a a mentioned above) also works.  I would use direct selection of device as the last alternative as this won’t work for everything.

That should work unless bedroom 3 was set to a local only source that couldn’t be routed to the kitchen.
can you manually do that scenario?
Room Control driver per room would be the alternative.

I think the best way to do this is with the Media Scene Agent. You’ll need to create a media scene for each scenario (group of rooms, primary starting room) you want.
 
If your matrix doesn’t have enough ports and C4 sees these as 2 separate/independent sources, you’ll then need to create custom programming to manually switch the second room to the required physical input / source device. Not the media stream, but the source device.
Getting a bigger matrix will ultimately be a more consistent and flexible solution.
 
 

I had issues posting at the beginning of the month - all my posts (including responses) would duplicate and then be deleted. 
I've just been advised that the issue is now resolved. This response will be a test of that.

I had issues posting at the beginning of the month - all my posts (including responses) would duplicate and then be deleted. 
I've just been advised that the issue is now resolved. This response will be a test of that.