powershell scripts runs but does not install .vsto package

I have created a PowerShell package to install an Outlook Plug-in. The script runs and is reported as a success but installing the .VSTO package does not occur. We install a certificate and download all the required files to the local PC but the plugin is not installed. If I run the PS script directly on the PC the entire operation runs and the plugin is installed. Is there something I need to do to allow the .VSTO file to run?