"Syncing data for..." infinitely loads. Can't play any of my XBOXONE games (though 360...

I had everything in this post nicely formatted with easy to read bullet points and stuff, but when I hit 'submit' the forum mushed everything together into a single block of text. I have gone back to at least add some line breaks and make this more readable.

I'm having issues with "Syncing data for..." infinitely loading on my XBOX ONE X. Here are the details so far

Notes:

This started Thursday evening This is the only XBOXONE we own, so this isn't an issue of two XBOXs not syncing with each other Aside from installing a few GamePass games earlier Thursday, nothing changed on this XBOX nor our Router nor our ISP. All diganostics
for the XBOXONE, Router, ISP show up green and there are no server issues publicly known at the time affected. I did notice that my network NAT type was 'Moderate' not 'Open' when I ran tests from the XBOXONE. So I went through my router and changed settings,
hard reset my XBOXONE (with physically unplugging my XBOXONE for five minutes, clearing the cache, etc) and NAT type now shows up as 'Open' but the problem remains unaffected.

XBOX360 games on both of our xboxlive accounts (there are two of us in the household that use it) all work and access the cloud just fine Except on my boyfriend's xboxlive account for Fallout New Vegas (which was when we first noticed all of our issues Thursday
night); that one crashes every time it tried to talk to the cloud, even after fully deleting the game and it's data/saves from the hard-drive and reinstalling. Works fine for me and my account (same account I am posting this via) though. Every. Single. Other.
XBOX360 game, on either of our accounts, loads and saves to the cloud just fine. Works perfectly normally.

By contrast: all XBOXONE games for both accounts have the syncing issue. Load them up, and right before the main menu the "Syncing data for..." window pops up I have tried just letting it go on and on for like 10 minutes, even with a tiny game (with tiny
save files) like Gato Roboto. Nothing. The bar just infinitely flashes from left to right, no progress, no completion, no matter how long we wait. If I hit 'cancel' during this popup, I get the option to 'keep syncing' (which just brings me back to the infinite
loading bar) or 'stop syncing' which drops me back to the screen before the main menu. Trying to go from here to the main menu just makes the popup pop up again. Well Battletoads, which was the game I just installed earlier on Thursday afternoon well before
the issues manifested, is a little different. It doesn't have the usual "Syncing data for..." screen with a progress bar and option to cancel; it just has a "accessing save data" screen with no options or progress bar, but it just sits there doing nothing
just the same). It worked fine earlier in the day when I installed it though I tried deleting all files (including save data files) for a couple games, uninstalling the game, then re-downloading/installing the game and starting it up again. No change, the
issue persists the same as before.

I noticed that most of my games, when I go in to "Manage game & add-ons", don't have anything listed under "Saved data", which is where game saves would go. Despite being played a bunch and having multiple games saved for them. I assume all this is in the
cloud somewhere only? Or maybe the files on the physical drive somehow got disassociated? Only a fraction of my games have anything in this section, and usually no more than a few megabytes, a few only in the kilobyte range. The issue doesn't seem to make
a difference in regards to whether the game (and it's data) are stored on the internal drive or an external drive. Either way, 360 games work fine, XBOXONE games don't work at all.

:)