I know generally what it's about but I don't know how to fix it. If you want to read about Windows certificate store and tell me, I'll do it.

The clickonce installer is looking for my public key to add it to the installation package. That key isn't part of the source code. It's something (I think) that Windows keeps in kernel mode data structures on the PC where I build Mojo. There must be some way to export it to other PCs but I don't know how.

It might be easier to use your own certificate. Visual Studio will make one for you when it builds the installer if you select an option or press a button in "Properties" in the MojoInstaller project. I forget how to do it exactly but it's very easy. Only thing is, though, if you do that and you distribute Mojo to yourself you may screw up your Mojo installation since ClickOnce may think the key is wrong.