Unable to access ipad due to icloud sync message

When touch the ipad screen to try and open it, a message comes up saying "some icloud data isnt syncing, passwords and data from health and maps cant be accessed on this device". It presents me with 2 option buttons: " not now" and "resume data sync". Neither of these buttons work. I've short pressed, long pressed, held. Nothing.

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It also won't let me turn my ipad off completely to see if a restart works, I can hold the off button down for minuets and nothing happens. do I wait for it to run out of charge? I could be here days!