Achievements not unlocking or tracking

I know there are other posts on this topic because I have read most of them (official Xbox support, xbox.com forums, trueachievements.com, reddit.com, etc.). However, none of the solutions have solved
the problem I am facing.

In a nutshell, the achievement system on the Xbox One and Windows 10 has stopped working for me. Period. Since February 11, 2019, I have not been able to unlock an achievement on either of those platforms
even though I have met the requirements.

I am not facing a “Done ... unlocking” issue. The system simply does not track any progress on any game I play.

I am playing online, and my progress is being saved in the cloud -- I see the save being synchronized when I play the same game on another console, and the game state is up to date on the new console.
As mentioned, the achievement progress simply is not being tracked for my gamertag.

For example, in the game “Gems of War”, my current player level is approximately 307, but looking at the game statistics
for my profile
on xbox.com it is stuck at level 262. Specifically, for the “Master of Strength” achievement (Reach level 500), my progress is only 52% (it should be about 61%).

Another example is the game “Rocket League”. This specific
case is not related to progress, but rather a one-time event that should have unlocked an achievement but did not. I completed
a 3v3 game, but the “Triple-Threat” achievement did not unlock.

I can add many more examples, including Windows 10 titles (like “Fallout Shelter” and “Microsoft Solitaire Collection”), but this post is already long enough.

So far, these are the things I have tried (unsuccessfully) when attempting to fix this issue:

1) ensure I am NOT playing in offline mode

2) exit games with the “menu -> quit” method to force a synchronization

3) reboot/restart the console

4) power off the xbox console completely (hold power button for 10 seconds)

5) power off the xbox console completely (hold power button for 10 seconds), then unplug the power cord for 24 hours

6) play on another console

7) remove my account from the console, reboot, re-download it, and try again

8) remove specific game titles, re-download, and try again

9) perform a soft factory reset on the console (keep all apps and games)

10) perform a hard factory reset on the console (remove all apps and games), re-download, and try again

It seems to be a synchronization problem with my account, not a problem connecting to Xbox Live. If it were a network issue, then achievements would still track and unlock locally. Another reason
I do not believe it is a network issue is that I can still use the cloud for saved game synchronization. I can also participate in party chat and play online ... only the achievements (tracking and unlocking) seem to be affected.

There is one more odd thing to note about this problem -- achievements still work on the Xbox 360 platform. I can even unlock achievements for a 360 title while playing in backwards compatible mode
on an Xbox One ... just not for any Xbox One or Windows 10 titles.

For what it is worth, here are some more details:

- Xbox One X (primary console)

- Xbox One original (secondary console used to test game synchronization)

- both Xbox One consoles have games stored on external hard drives (I have tried disconnecting and using internal storage with no difference)

- both are connected via Ethernet (I have tried WiFi with no difference)

Is there …

- anybody who knows why this happens?

- any other suggestions for solutions/fixes that I can try?

- any other information I can provide to help diagnose the root cause?

Any help is appreciated ... this is really quite frustrating.

Thanks.

:)