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What is the exact message you get, when you try to sign in to iCloud, please?
OK. That means you will need to reset your Apple ID, quite simply. (The Apple ID becomes locked, when your account has been attempted to be accessed, e.g. by entering the wrong password, too many times. Someone may have been attempting to hack your account that way... unless you yourself were the one entering unsuccessful passwords too many times of course.)
The process may be summarized this way:
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