After a new installation of the Citrix Online Plugin v12.3.8, I went to launch an application from the Citrix Portal. Needless to say, it failed to launch with the error message above. If you press OK, a window pops up asking you to browse to the “ICAWebWrapper.msi” location. Not knowing where the MSI is located, I tried re-installing the plugin thinking it would be an easy fix. I got the same message again.
After about an hour of troubleshooting, I finally figured out this very simple fix: