PS. I don’t know how familiar you are with Authenticode signing, but please do read up on time-stamping your signatures. This prevents the installed apps from going out-of-date when the certificate used for signing expires.
Oh, some confusion on my part: won’t the installer exe run, or won’t the plugin run, without a digital signature?
If it is only the installer that is giving problems, you might be better off just making an MSI installer, instead of an exe installer. This is what we do, and there is no need for a digital signature on the MSI.