I lost everything

Yes, that is the same as others are getting. I’m going to move your topic into the other one. It seems as of now there is no work-around for it. But keep following this topic:
https://forums.flightsimulator.com/t/unable-to-sync-your-data-with-the-cloud-after-a-reinstall/383497

Make sure you also submit this to Zendesk.
https://flightsimulator.zendesk.com/hc/en-us/requests/new