Hey mate, the private key (Password) that you use to log into the account can be manipulated by the browser or OS when sending across the environment. Meaning that when it's received it's not received in the right format and thus rejected.

Worth trying on a different and updated device.

If the feed back from the Steemit system is that the account hasn't changed then I would think that there is an error in the data being paraphrased. Otherwise I would ask the Steemit team if the password has been changed recently, if it has, then you have your answer and the account is gone.

If it hasn't then it is simply a matter of getting the private key through the verification process correctly.

Big fan, hope you get back in.