Same issue over here. Installed it today in my F:-drive, with MSFS 1.29.30.0, which is on my G:-drive. Once I start a flight, cliclking on the XEnviro button in the toolbar, it tells me there's no connection and that I have to start the application, which is already running hopwever. ( started a Admin ).
The solution on the Enviro known issues pages is this: "No connection with Microsoft Flight simulatorSolution:Please make sure you don't have any addons that alter flight simulator ToolBar appearance." Huh? What do you mean? Do I have to uninstall other plugins like GSX Pro, Navigraph and more??? That would be ridiculous