Sim Stuck Loading on Blue Bar

Asobo have acknowledged this as an official bug with the sim and have provided the following guideance:

"We are currently looking into this issue. In the meantime, if your sim stops loading and the blue bar gets stuck, please try the following workarounds:

Exit out of Microsoft Flight Simulator (Alt+F4) and relaunch the title one or two times

Try running the sim as an Administrator

Here is another workaround:

1. Check your Roaming directory (e.g. C:\Users\<UserName>\AppData\Roaming\Microsoft Flight Simulator. If you see UserCfg.opt, open it and verify that InstalledPackagesPath is set to a path you wish to install your game. (e.g. “D:\Game\Microsoft Flight Simulator”)
2. Delete everything else in C:\Users\<UserName>\AppData\Roaming\Microsoft Flight Simulator
3. Start the game again. It should prompt you to select a storage location. If your UserCfg.opt has the InstalledPackagePath set, then the file path of the directory you specified should appear in the text box.
4. Press Update. It should transition to a screen where you can actually see what files are being downloaded from the server."

More information: https://www.flightsimulator.com/known-issues/