White screen after update
Most likely, you did not use binary transfer mode for uploading new theme version.
So delete theme via FTP and upload it again using !binary transfer mode.
When upload is complete, go to Appearance > Themes in your WordPress admin area. You will see new theme there. Hit Activate to activate theme.
If these actions do not help to solve problem of white screen, you should open file wp-config.php, find string
and replace it with this one
Now you’ll see error on your screen, which helps you to recognize a real problem.