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# Microsoft .NET Framework 3.5 is missing

### Issue Description: 

While attempting to install STPISecure, an error message is displayed: 

 ![](https://content.gitbook.com/content/70eSU57m5853RfAjtrLZ/blobs/71yZwq9nSj4N53HBOcty/image.png)

STPISecure requires Microsoft .NET Framework 3.5.

Please use Windows Update / Windows Features to install this version, and then re-run the installer.

**Solution:**

 Install Microsoft .NET Framework 3.5 through Windows Update or use the "Turn Windows features on or off" option from Add/Remove programs to enable .NET Framework 3.5.

 ![](https://content.gitbook.com/content/70eSU57m5853RfAjtrLZ/blobs/DdY8kO9UUAn57II8Z9zY/image.png)

  ![](https://content.gitbook.com/content/70eSU57m5853RfAjtrLZ/blobs/6FAwh89wypriqaLVPKUD/image.png) 

Once Microsoft .NET Framework 3.5 is installed, retry installing STPISecure.