All guys having issues switching between spotify/tidal/aiplay or zen stream disappearing from found devices and etc.. Forget controlling your zen stream via web ui, use connection via ssh and simply restart your services there. It is by far the best and quickest fix to majority of your issues with this streamer. Zen OS is volumio which has lot's of quirks and works well if you don't touch and switch between connections, but otherwise you can quickly run into issues.
First enable ssh connection via developer mode. I think it's -->
http://ifi.local/dev or http://ipaddress_of_your_zen/dev
You can find ip address of zen stream running "arp -a" command via cmd windows/terminal mac os or find ip address via web interface somewhere in the settings.
For windows you will have to install putty, mac users can simply use terminal --> via putty "volumio@ip_address_of_zen"
via terminal "ssh volumio@ip_address_of_zen" Password is "volumio" as well
You can list all services and read of what things do --> systemctl list-units --type=service
If you have issues with tidal -->
systemctl stop ifi-streamer-tidal-connect.service
systemctl start ifi-streamer-tidal-connect.service
or simply:
systemctl restart ifi-streamer-tidal-connect.service
For spotify just replace it with "ifi-streamer-spotify-connect.service", airplay "shairport-sync.service". I have 0 issues controlling zen stream via ssh. You can reboot it via ssh and do lot's of stuff there. It is stable and responsive unlike access via http.
By the way airplay 2 is released on shairport beta deamon, but I was not able to get it running as volumio has missing dependancies and I couldn't work around them