Developers creating MSIX packages with the Windows Application Project (WAP) need to provide a code-signing certificate with an additional field not needed when creating packages through other means. Specifically, it needs the BasicConstraints field in the certificate.
If you purchase a code signing certificate from a Certificate Authority, this field should already be there. But in this case I was …

PsfTooling is the free tool to work in conjunction with the Microsoft MSIX Packaging Tool.
The Package Support Framework (PSF) was originally an open-source project to help Win32/DotNet applications run when inside an MSIX Container. TMurgent has taken up the support for the PSF in our own fork 

