There are several reasons why you may suddenly be unable to access wp-admin. A blank white page may be showing, or there is an error page being displayed. The most common reasons for this include an issue with your theme, a problematic plugin, the wrong permissions set in your cPanel, corrupt files in your WordPress installation, or even your firewall preventing you from accessing it.
Navigate to the wp-admin folder of your WordPress installation.
Make sure the permissions are set to 755 for folders and 644 for files
Check Your Firewall
Disable your firewall temporarily and see if you can access your site. If you can, enable the firewall and add an exception for your URL… how you do this will vary according to which firewall you're using.
Check Your Files
Try to go log in at yoursite.com/wp-login.php instead of yoursite.com/wp-admin. If that works, something may have corrupted your login folder. Download and unzip the latest WordPress files and replace your current wp-login.php file with the new wp-login.php file.
If you should have any questions, would like assistance or this guide does not work, please contact us through Live Chat or by submitting a ticket with our Technical Support team.