- Plesk for Windows
The "403 Forbidden" error is shown when the Default documents option is set to Default under Domain > example.com IIS Settings .
The "Default Document" feature becomes disabled in IIS Manager. This is Plesk bug with ID PPPM-6119 which was fixed in Plesk 17.8.
Upgrade to the latest Plesk version.
As a workaround, go to Domain > example.com IIS Settings and enable Enter custom value for the Default documents option: