The most common reason when people cannot login and receive message that password incorrect - they are trying to login in wrong place.

                                                                                                   For account model 

                                                                                             For wallet model 

                                                 nobody can change your password except you

                                                password is not changing by itself

You can login with ACCOUNT MODEL here with login and password

You can login with WALLET MODEL here with your backup file and password

Please note: if you try to login using correct password in incognito mode ( google chrome) there won't be any issues.