We have put together a tool that should find and remove the installation folder and allow you to install a new version without any problems.
The Tool can be downloaded from here:
Make sure you have closed any running installers and the add/remove programs window then run it as administrator (i.e. right click > Run as Administrator) for it to be able to remove the folder.
It will list any of your JF MSFS2020 products it finds in your add/remove programs list. One just needs to select the entry you are having problems with a use the delete button.