The question would be: how did you uninstall it at first ?
If you got the MS Store version, then there is a precise way to do things in order to install or update the sim properly.
Dave gave quite a few good tips above:
- you MUST ensure your windows is up to date,
- you have to download and install the latest version of the "Xbox application" from the MS Store app, and after installation, you have to run it at least once.
- in the MS Store app, you have to ensure you got all of the applications up to date (click on the dots in the top left corner, select downloads and updates, and then press the button "get updates". If you have installed/updated and launched the XBox app, it might be able to find an update for MSFS
From there you should be able to install the sim properly.
A computer restart might be necessary prior to do that.
A log off then log on to your MS Live account might be necessary as well.