I noticed somehow when upgrading WordPress to version 4.7 that after the update wp-admin does not open, instead of the admin window there is an empty window and in the address bar of the browser the following address:
Hence the conclusion – automatic updates are not always successful.
The problem is that the version of the database in the /wp-includes/version.php file and in the WordPress database are not the same in the wp_options table.
In my case, the versions in the file and in the database after the update were indicated as follows:
$wp_db_version = 38590; db_version 37965
Therefore, to solve the problem in the wp_options table, where db_version we specify the same version as in the /wp-includes/version.php file.
After that, wp-admin will open.
Well, to find out why it happened, you need to look at the errors in the web server logs.