Ah, I see you’re way ahead of me. Publisher mismatch is indeed the normal reason for that error. Have you tried manually running SignTool with the debug option?
C:\Program Files (x86)\Windows Kits\10\bin\x64\signtool.exe sign **debug** /a /f "D:\MyGame_416_uwp_merge\ueproject\Build\UWP\MyGame_temp_cert.pfx" /fd SHA256 "D:\MyGame_416_uwp_merge\ueproject\Saved\StagedBuilds\UWP64\MyGame.appx
As for the generate button, it should be on the UWP page of project settings, in the packaging section, and look something like
Can’t think of any reason why it wouldn’t be there for you - it’s unconditionally added to the layout. I did realize while grabbing that for you that it’s a little fussy right now - you need to delete the existing .cer, .pvk and .pfx before it will work, and if you change publisher/identity/name you may need to close and reopen the settings window before trying to generate.
One last thing - I see you’ve changed the file name of the certificate in use (not Build/UWP/SigningCertificate.pfx). That ‘feature’ didn’t seem particularly useful, and wasn’t ever exposed through editor UI, so it’s gone in the latest and we just always use the default location. Don’t think that’s related to your current error since the command line to signtool indicates your custom location is in use, but it might become relevant as you try to make changes to pinpoint the problem.