most wireless keyboards connect to iOS device via Bluetooth, and Bluetooth can sometimes go a bit wonky - even on Windows and on Android devices..
first.. shutdown the iPad or restart it.. hopefully the keyboard would resume after starting-up the iPad - give a reasonable 20 seconds to allow the iPad to connect to the Bluetooth keyboard after restart..
also make sure that the iPad had received the latest updates from Apple - this is a small and an unlikely cause for the problem, but it can happen..
meanwhile, check the batteries on the keyboard, because you will look foolish if your main problem was a low battery issue.. and you will look extra foolish if it was switched off..
if there is no response from the keyboard, then you need to delete the old Bluetooth connection and reset a new fresh connection..
or in experts' language of so-called geniuses at Apple, "unpair the Bluetooth device and pair it back, duh!!"..
so go to the settings, tap on the 'General' tab, and tap on Bluetooth..
you should be able to locate the keyboard in the list of connected Bluetooth devices..
it may appear as "apple Keyboard", or as "Bluetooth keyboard" or even some generic model number on the keyboard, such as '3POSUCKSBALLS'.. depending how cheap you were.. LOL..
you need to tap on the keyboard in the list, and tap "Forget" to "unpair" the said Bluetooth device from the iPad..
to ensure maximum results, restart the iPad by pressing the power button and shut down the iPad and restart back on again.. and then tap in the Settings on General and Bluetooth, as we did just now..
next, put the keyboard in the pairing mode - usually by long pressing the Bluetooth button on the keyboard until the LED light on the keyboard starts blinking.. and wait until the name keyboard pops up in the list of detected Bluetooth devices..
tap on the keyboard from the list to connect.. you may need to type some numbers on the keyboard, such as 1234, and viola!!..
if the keyboard does not show on the list of the detected Bluetooth devices while pairing (wait for a good 20 seconds), then first try refreshing the list of Bluetooth devices by closing down the Settings and re-open the 'Settings' and re-open the 'Bluetooth' settings..
if the keyboard still does not show in the Bluetooth devices list (again, wait for a good 20 seconds), the keyboard itself could be faulty or was put too far (should be within 30 feet from the iPad).. so you may want to retrace back the steps again before calling for Apple tech support..
like i mentioned,
this is a common problem in other devices running Windows, Android and such.. and it is a common problem with other Bluetooth devices, such as hand-free headphones and game controllers..
personally, i try to avoid using Bluetooth whenever possible..
all the best..