There are a number of reasons you might get a 403 Forbidden Error. That error occurs when your browser makes a request to the server, but the server refuses to display the page you requested. This could mean that you do not have permission to view the requested page, which may indicate that there is a configuration that needs to be changed on your site’s server.
Here are a few troubleshooting steps:
Before making any changes to your site’s files I would recommend making a backup so you at least have a point you can fall back to if something goes wrong.
Update All Plugins, Themes, and WordPress
Make sure you are running the latest versions of all plugins, themes, and WordPress core files. If you need help updating, take a look at this article.
Rule Out Other Plugins and Themes
Deactivate all other plugins, and revert to the default (TwentyFifteen) theme, then try again. If you don’t get the 403 error, try re-activating plugins and themes one by one and re-trying the steps you used to get the error in the first place until the error comes back. The last plugin you reactivated may have been the cause of the problem.
Replace Core WordPress Files
Follow the steps here to replace the existing WordPress files on your server. Your site may have a problem with one of the core files. Deleting the wp-admin, wp-includes directories, and any other loose files and replacing them with a fresh copy will eliminate any problems with the files on your site if there is one.
Check File Permissions
Directories, and files can have different permissions. If they are configured improperly you may end up not having access to the page you are attempting to view. Check the WordPress Codex for Changing File Permissions to use as a guide. Your host may also have modified permissions for some directories or files, so you may need to check with them for help.If you are unfamiliar with changing file permissions, you can use this guide for help. Your host may have other methods for accessing files other than cPanel, so check with them if these steps don’t help.
Check Your Site’s .htaccess File
There might be a rule in there that is causing you to receive this error. A basic .htaccess file would have code like what is found on this page, although some plugins add their own rules to this file so yours may look different. You can start by replacing what yours has with what was found on that page to see if it helps.
Ask Your Host
Your hosting account may have rules set up such as mod_security, which could cause this error.
