Activation lock question

See Turn off Activation Lock https://support.apple.com/en-us/HT201441. If you acquired your device second hand from an individual (almost invariably not the prior legal owner), you will need to obtain the needed password from the prior legal owner (almost invariably not the seller) or have the prior legal owner sign out of iCloud; erase the device; and remove it from their device list. If you cannot do so, then the device is useless to you.

Kiss you money goodbye. You've been scammed. File a claim with eBay to get your money back.

Activation Lock Problem

If you purchased the device second-hand, then it is useless without the Apple ID and password to which it is locked. If you don't have it, can't remember it or cannot get it, then the device is useless to you. Try to get your money refunded, if you can, or take it to an Apple store for an exchange provided they will help you. If you are the original owner, then take the device, a copy of your purchase receipt and identity proof to an Apple retailer where they may be able to assist you. For a deceased owner see How to request access to a deceased family member's Apple accounts - Apple Support. Note: there is no guarantee that anyone can gain access to the device.

About Activation Lock on your Mac - Apple Support.

Activation Lock - Turn off Find My iPhone.

About Activation Lock on your Apple Watch - Apple Support.

Turn off Activation Lock - Apple Support.

Need  to  disable  Activation  Lock  on an  iPhone  or  iPad?

Nothing can be done, your device is useless and can't be unlocked

You would need to try and return it or get the owner to unlock it