You go to a WordPress built site which was working fine before and see white screen only or broken layout without images, all messed up etc.
Here is the first thing to check:
- Go to sites files via FTP software FileZilla
- Do not touch core Genesis or twentysixtenn/fifteen etc themes.
- Define which child themes are installed
- Download them from StudioPress (or OptimizePress – rare case)
- UnZIP and upload to server rewriting current files of the same theme
- Download fresh version of WordPress, compare files and delete any suspicious.
- Reload all files of fresh WP installation to the server. IMPORTANT: DO NOT TOUCH wp-content folder and wp-config.php file