Hello Marcus,
Not sure if you have fixed this issue yet, but I had a similar problem of the Sim and / or its cloud-based game saving not totaling up my accumulated flight hours. The logbook would log them, but my Sims Profile page was only showing the total hours up to a certain time period. I referred my issue to a Zendesk ticket and Stetson with Microsoft Flight Simulator Support responded straight away. He had several suggestions toward a solution, but the one that nobody ever keyed on was what fixed mine.
Assuming that you are running MSFS on a windows based PC:
On your windows taskbar, click on search (cortana, box, or magnifying glass), type services. In the top results you should see Services (as an app). Click on it. Go to all entries that relate to Xbox. On my Windows 11 I have 4 - They are:
Xbox Accessory Management Service
Xbox Live Auth Manager
Xbox Live Game Save
Xbox Live Networking Service
Make certain that all 4 have a STATUS of RUNNING and a STARTUP TYPE of AUTOMATIC or Automatic (Trigger Start )
Mine were all set to a Status of Stopped and Startup Type of Manual. Once I changed them to what Stetson suggested, my flight hours started adding up again. I did however, lose all my previously logged flight time. It’s there in the logbook, but not being added up, just the new flight hours are. Which I am fine with.
Hope this helps you and anyone else out there that is experiencing the same issue.
~WEB~