WordPress Error: Database Update Required

Solution1:

This is due to a missmatch between the databases versions you said you are using in the settings.
Please follow this steps:

1. Go to /wp-include/ folder and open the version.php.
2. Find the value for $wp_db_version, and write it down.
3. Now, open your database, check in the table called wp_options
4. Find the db_version value:
   SELECT option_value FROM yourdatabase.wp_options WHERE option_name = ‘db_version’;
5. Those two values must be the same. Change it in the version.php file, not the database.

Solution2:

Restarting php-fpm service helped me, it clears cache on restart

sudo service php5-fpm restart

Hope that helps some folks out there.

Solution3:

1. Try clearing your browser cache
2. The option db_upgraded isn’t getting set by the upgrade process. Try this: go to /wp-admin/options.php. Fill the field db_upgraded with a 0 (zero). Hit Save Changes.