The commands that typically work are, in order of preference:
svc power reboot
am start -a android.intent.action.ACTION_REQUEST_REBOOT
setprop sys.powerctl reboot
You’ll need to ensure the device is rooted for these to work, and that Xibo for Android has been granted permissions to run as root (with your su manager).
You simply then enter that command in to the display settings profile for Android devices, inside your reboot command. Once entered, you’ll need to allow the Players time to collect that new information before they will start using it. You can tell if they have picked it up when the last connection date changes on the Displays page.
Commands are sent by XMR, so it’s worth requesting a screenshot and checking that comes back straight away to ensure XMR is working and configured correctly.