Here is a procedure I developed from “fixes” that have been posted here on the forum.
Some of this is a duplicate of things in the Zendesk article.
It may be some help.
Ensure all addons are removed from the Community folder, and any 3rd party plug-ins such as Navigraph etc., are uninstalled.
Remove any overclocks you have set up.
If you have used the Google map replacement, uninstall it using it’s uninstaller.
Ensure any third party antivirus programs (Avast, AVG, etc) are shut down.
Ensure you have an open path through the Window’s firewall.
Ensure all Windows updates are installed.
Make sure the time and zone in your PC settings are correct.
Sign out of the xbox app on your PC, and shut down Xbox app.
Sign out of MS Store App, and shut down same.
Shut down computer.
Unplug all controllers, except mouse and keyboard.
Restart computer.
Open and sign into Xbox app.
Open and sign into MSStore.
Reboot computer again.
Try sim.
Plug in controllers.