Symptoms
Plesk interface displays the below error:
HTTP Error 500.0 - Internal Server Error
<handler> scriptProcessor could not be found in <fastCGI> application configuration
Cause
'PleskContolPanel' Website is configured improperly. Some of the request handler points to the non-existing binary.
Resolution
Make sure that all request handlers in 'PleskControlPanel' website have correct paths.
in case if this doesn't help, make sure that there is no 'web.config' file in the '%plesk_dir%\admin\htdocs' folder