Microsoft Sudoku has once again lost my progress on daily challenges. Please advise when this issue will be fixed and my progress will be restored.

I think I've found the answer as follows:

Having tried the proposed solutions as above, I went for a "last ditch, last chance" solution before ditching SuDoku for good.

So I deleted the SuDoku App AND .... having wiped the 'Identity Provider' folders referred to above, I also deleted XBox.

I then re-downloaded and installed MS SuDoku from the Microsoft Store.

I DID NOT and HAVE NOT reinstalled XBox.

And SuDoku is now working perfectly, and has been doing so for the past few days.

Since then, I have NEVER received any notifications that I am offline.

Seems to me that rather than the SuDoku App, the problem lies with XBox

As of today everything seems to be fixed. Sudoku remembers my Sudoku level when I exit and re-enter the game. Plus, it now remembers if I have a game in progress and exit Sudoku. When I come back in, it remembers the in-progress game and restores it to where I was at the time. Glad that everything now seems to be working as intended.

Looks like its fixed for me...
Hope its the same for all of you guys !!

I tried these steps and it made no difference.....

I had a sudoku score of over 230, as far as I remember, and I was logged in when I started sudoku. I got a question regarding my sudoku skills, and answered it. For some reason the game selected an easy mode by itself, so I solved it quickly, and got a score of 1! The above solution did not help me since this new score was saved when I finished the game.