Activation Required

While writing an essay for class my IPad mini 3 randomly said “activation required”. I was confused so I did a hard reset to see if that would fix it so it didn’t so I just entered in my information and it let me log in. My iPad mini 3 is running on IOS 9.3.4 what would cause the activation required to pop up? My iPhone 6s running on IOS 11.1 didn’t have this issue and they share the same Apple ID.