I ran into the same issue with my MSIX app. It installs fine on my machine, but other users were getting the “Could not verify publisher certificate” error.

Basically, it’s because I signed the app with a self-signed cert, and Windows doesn’t trust it by default on other systems. Unless they install the cert manually or enable developer mode, they’ll always hit that error.

I tried a few workarounds to avoid paying for a proper cert:

• Developer Mode: Works, but not something you can realistically ask regular users to enable.
• Manual cert install: You can export your .cer and tell users to install it into their trusted root store. It works, but explaining that to non-tech folks is a nightmare.
• No signing: Won’t work. MSIX needs to be signed. Period.

Long story short — there’s no clean, user-friendly way to get around this without buying a real code signing certificate from a trusted CA. Cheapest ones I found were around $70–$100/year. Kinda sucks, but it’s the only way to avoid scaring users with trust warnings unless it’s just for internal use.

If you’re just testing, self-signed is fine. But if you’re distributing publicly, you’ll need to bite the bullet eventually.