Once confirmed that the Xbox is connected to the internet (from Xbox and double check within MSFS that the marketplace is not disabled/greyed out), the silly thing that worked for me was to disconnect the cable (or switch off wifi), and after that shutdown and restart Xbox and MSFS while not connected to the internet in any way. Then MSFS will give a message that you are offline, and can it continue in offline mode? Continue with loading/starting MSFS in offline mode**.
**The offline pack must be installed for this to work.
Then again shutdown MSFS/Xbox, reconnect the cable or restart wifi (if wifi, then with confirmation that wifi has full booted up with a check by loading any webpage from some other device) and then restart Xbox/MSFS.
Pray hard to the good kind and merciful lord.
On this attempt the marketplace, and the options to toggle data within MSFS will hopefully then be available.
An approximate of this worked for me. Hope it works out for you too.