> For the complete documentation index, see [llms.txt](https://docs.payfacto.com/payfacto-knowledge/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payfacto.com/payfacto-knowledge/canada-doc-center/applications/secure-payment/application-securetable-module/troubleshooting/microsoft-.net-framework-3.5-is-missing.md).

# Microsoft .NET Framework 3.5 is missing

### Microsoft .NET Framework 3.5 is missing

### Issue Description:

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

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.

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