– Fatal error in the output generally indicates either your theme doesn’t like your version of WordPress, you have a plugin that doesn’t like your version of WordPress, or you have an incomplete install/upgrade.
so, try:
-switching to the unedited default theme (that came with your version of WP) for a moment by renaming your current theme’s folder in wp-content/themes. The idea is to force WordPress to fall back to the default theme to rule out any theme-specific issue.
If you don’t have access to your admin area, then access your server via FTP or SFTP or whatever file management application your host provides.
– resetting the plugins folder by FTP or phpMyAdmin.
-If the above troubleshooting steps do not resolve the issue, re-upload all files and folders EXCEPT the wp-config.php file and the /wp-content/ directory from a fresh download of WordPress. This should replace your core files without changing your content and settings in wp-config.php file and the /wp-content/ directory.
