Symptoms

Changing ASP.NET setting for domain is showing the following error in Plesk Panel:

ASPdotNet() constructor failed: Unable to getDomainConfiguration: aspnetcfg failed: Can't detect .NET version. Possible site does not use ASP.NET
---------------------- Debug Info -------------------------------
0: ASPDotNETUIPointer.php:69
    ASPDotNETUIPointer->accessItem(string 'GET', NULL null)
1: UIPointer.php:600
    UIPointer->access(string 'GET')
2: plesk.php:50

Cause

Missing ASP.NET handler for the domain in IIS configuration.

Resolution

1. Open IIS Manager ( Start > Run > inetmgr ).

2. Select problem domain and open "Handler Mappings" .

3. Press "Revert to parent" 

If steps above were not helped. Refer to this article