Activation required

An interesting thing happen while using my iPad which I bought new and own for several years in the middle of my program my iPad automatically locked out and prompted for ‘Activation required’ this never happened before so I followed the instruction to unlock but it won’t unlock because it’s not recognizing my information when I click on help it states that ‘the owner has used Find my IPhone to link to their Apple ID’ my iPhone is with me and I never used this function it concerns me that my iPad serial number might be duplicated. Any suggestions as to what I should do