Admin user is unable to login I've just changed the view of login form to Drupal default view. Now I am not able to log in as administrator. 

I have tried to change the password using php .\scripts\password-hash.sh newpwd.  I got an hashed password, I used to update the password stored in the database with a SQL query, but still I am not able to log in. I have also cleared entries from flood table.

Any help will be appreciated.
Please check if you are using the correct username (you can see that
in the database).
Try to use the "Forgotten password" function to reset your password
Check the last entries of the watchdog table to see if you can get
more information from there
Check your server logs to see if you get any error there (under Linux
this would normally be somewhere under /var/logs).
Install drush and use that to very easily log in
(https://drushcommands.com/drush-7x/user/user-login/)