Flight Simulator gone after update yesterday

User Support Hub Crashes (CTDs)
7

Sim doesn’t start any more after 2024-10-01 update - Remove Navigraph AIRAC Cycle - Bug Reporting Hub / Crashes (CTDs) - Microsoft Flight Simulator Forums

skip to close to the end of the above thread for a probable fix for this issue.

In short, if you uninstall Navigraph nav data, via Navigraph hub, if you have it, you should be able to get MSFS up and running.