Have you changed your Apple ID or password since then?
Read this link and learn "What to do after [or before] you change your Apple ID [email address] or password" --> https://support.apple.com/HT204071 - "After you change your Apple ID email address or password, you might need to update your sign-in information with any Apple services you're using."
- You may also wish to turn off "Find My" before changing information and turn it on again afterward.
Have you tried any old ID and password?
Contact Apple for support and service --> "See a list of Apple phone numbers around the world." Click here --> https://support.apple.com/HT201232
Otherwise:
- Apple can remove a lock if a person can provide sufficient evidence of valid ownership. Do this online here --> https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not state what constitutes proof. Prior to this new online service Apple typically required the original receipt issued by an Apple Authorized dealer and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership).