Chromecast with Google TV Mirroring Blocked

[bradocchs]

I'm the Tech director for a high school that uses an all Meraki network. When we try to screen mirror using a Chrome browser cast, the Chromecast device (Chromecast with Google TV - gen 4) we want to mirror to says "Available for specific video sites" and is not able to be selected. I have verified that this functionality works fine on my home network, so I know something is being blocked on our Meraki network. All the devices in question are on the same default VLAN. I've already tried enabling Bonjour which actually made the issue even worse. The odd thing is that this functionality works great with our older gen2/3 models and seems to only affect gen 4.

Any recommendations would be greatly appreciated! Thanks.

[PhilipDAth]

Are the APs running a current stable firmware of better?

Under Wireless/Firewall & Traffic shaping (make sure you have the correct SSID selected), what are these settings like?

[bradocchs]

Yes, all up-to-date and settings are exactly as you show (we only have 1 SSID).