Hello,
You must contact Apple for help when you see a message saying "You cannot login because your account has been locked". This is not something you can fix yourself. Apple provides a contact link for this specific issue. Tap or click here --> https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362
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Based on the support article: If a message says 'Your account has been disabled in the App Store and iTunes' - Apple Support