A 403 means the server found what you asked for but refused to serve it. The three usual reasons are permissions, protection and blocking.
Permissions
Files should be 644 and folders 755. A folder set to 700, or a file set to 600, cannot be read by the web server. If you have just uploaded files, particularly from Windows or by extracting an archive, check these first.
No index file
If a folder has no index.html or index.php and directory listing is off, you get a 403. That is intentional.
Directory protection
If you have password-protected a folder in cPanel, a wrong password gives 401 but a misconfigured rule gives 403. See How to configure directory and file privacy.
Something is blocking you
A firewall rule, a security plugin or a ModSecurity rule may be refusing your particular request. The giveaway is that the site works for other people, or on mobile data but not on your broadband. In that case it is your IP address that is blocked, not the site that is broken.
If you think you have been blocked, open a ticket from a device that can still reach the client area and tell us your IP address, which you can find by searching for "what is my IP".
