Account involved on selling is hard to recover because there’s a chance that the old owner sell it intentionally and he wants to claim back the ownership after the sales by applying the benefit of the doubt that his account got hacked and sold by someone. Either way the account reputation is already a messed even if you recover or not.

Just like what @Maus point out, You should setup a strong password so that your account will not be easily hacked. Recovering a clean account is already hard process so what’s more for an account involved in account selling.