All versions - The Marketplace tile and/or Online services are grayed out

To fix this issue, simply restart Online Services and sign out/sign in again. 

RESTART DATA CONNECTION SERVICES

If Online Functionality is turned OFF, turn it back ON.

If Online Functionality appears to be ON already, restart the Data Connection Services manually.

• Launch Microsoft Flight Simulator
• Go to Options > General > Data
• Toggle Online Functionality, Bing Data World Graphics, Photogrammetry, Live Real-World Air Traffic, Live Weather and Multiplayer "OFF"
• Click on Apply & Save
• Toggle Online Functionality, Bing Data World Graphics, Photogrammetry, Live Real-World Air Traffic, Live Weather and Multiplayer "ON" again.
• Click on Apply & Save

Online Services automatically will also shut off when you have reached the monthly data limit. If your current Data Consumption is superior to the Data Limit you have set up:

• Turn Data Limitation OFF

or

• Increase the Data Limit (GIB)

SIGN OUT/SIGN IN IN

1. Click on your gamertag in the top right corner of the screen
2. Click Sign out
3. Close Microsoft Flight Simulator and wait a few moments
4. Launch Microsoft Flight Simulator again, and Sign in