If users are unable to access Biosite or for the Keyboard to be presented to enter their credentials, its likely not got a WiFi connection or 4G Signal.
If the tablet does not connect to Mobiles, it will need to go on to Guest or a 4G sim will need to be provided from Nuvoli currently.
This seems to be impact OS9 Android tablets and these cant be upgraded to 10 as they are tab 2's