Now try to publish the ClickOnce application. If you still find the same issue, please check if you installed the Microsoft .NET Framework 4.5 Developer Preview on the system. The Microsoft .NET Framework 4.5 Developer Preview is a prerelease version of the .NET Framework, and should not be used in production scenarios. It is an in-place update to the .NET Framework 4. You would need to uninstall this prerelease product from ARP.
https://blogs.msdn.microsoft.com/vsnetsetup/2013/11/18/an-error-occurred-while-signing-signtool-exe-not-found/
Lastly you might want to install the customer preview instead of being on the developer preview