If an IIS entry becomes corrupted or was accidentally deleted, it can be rebuilt via Plesk command-line:
Plesk < v11.5
"%plesk_bin%\websrvmng.exe" --reconfigure-vhost --vhost-name=example.com
Plesk >= v11.5
"%plesk_cli%\repair.exe" --reconfigure-web-site -web-site-name example.com