Hi,
Sorry to hear you're experiencing this issue.
Your progress is saved on your account, repairing and resetting the Sudoku app will re-sync the information from your account to your computer and will fix the problem.
1-Click on Start then click on Settings
2-Click on Apps
3-Search for the Microsoft Sudoku and click on that
4-Click on the "Advanced options" or "Modify" button
5-Scroll down, then click on the "Repair" and "Reset" button
6-Relaunch the Sodoku app, log in with your account and your progress should show correctly
I hope this information helps. If you have any questions, please let me know and I'll be glad to assist you further.