Blank Admin Area

Try manually resetting your plugins. If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, access your server via FTP or SFTP, navigate to /wp-content/themes/ and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue (theme functions can interfere like plugins).

Thanks James. I’ve changed the name of the theme and the site then goes down. I renamed the plugin folder and I now get this message when trying to log in:

Fatal error: Call to undefined function wp_is_mobile() in /home/cycling/public_html/wp-login.php on line 39

Ok, now try downloading WordPress again and delete then replace your copies of everything except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings. Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.