Please refer to this similar case for a hint:
Windows 10 Custom Credential Provider: Authenticate without Windows password
https://stackoverflow.com/questions/57121718/windows-10-custom-credential-provider-authenticate-without-windows-password
>Your provider must return to the Logon UI or Cred UI the authentication information. It can be a login/password pair or a certificate based authentication.
>Inside of your database you can store a real user's password and return it after checking your own OTP
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