Xbox App started misbehaving - error 0x80070057

Hi all,

I've been using the Xbox app for a couple of weeks now having got a voucher for purchasing an upgrade to my computer. Everything was going fine, started playing Sea of Thieves, Age of Empires I and Football Manager 20.

Starting yesterday, I received the following pop-up message when my computer turned on: https://gyazo.com/d95fa8225a5b99c090fbb64597a87a5a

I thought nothing of it and played a bit of Football Manager. Later on, I went to play some Sea of Thieves with friends and nothing was working. I tried to go into the Xbox app and the window appeared very briefly, then shut down immediately. I uninstalled
and tried to reinstall using the windows store and the same thing was happening. After scratching my head for a while and doing some googling, I found a site which suggested I go to command prompt and type the following:

icacls "C:/Program Files/WindowsApps" /t /c /l /reset

Suddenly, everything seemed to be working again, great! Until this morning that is, where I got the same error message pop up when my computer turned on, but the Xbox app was loading so I ignored it. When I went to try Football Manager, however, it kept
instead loading the Windows Store and asking me to download "Gaming Services", despite the window telling me that this was already installed. Nothing I tried was working so I thought I would uninstall and reinstall it, but now I'm getting the above error code.
Same no matter what I try to install. Age of Empires I had also stopped working so I tried to reinstall and am getting the same error.

Funny thing is though, despite my other installed games NOT working, Sea of Thieves is now actually behaving fine. I'm really at a loss to understanding this however I'm guessing something has happened to my /WindowsApps/ folder - this may sound desperate
but is there any way to completely remove everything related to this and re-install it?

Things I've tried:

Installing on to different drives/partitions

The "icacls" command as above.

Running the Reset / Restore options through "Programs and Features"

Running the Windows Store Apps troubleshooter in "Settings"

WSReset.exe

Installing the latest Windows update

Crying in a corner until it works

PC Specs are as follows:

AMD Ryzen 3700x

16gb RAM

GTX 2060 Super

3tb+ remaining hard disk space

Internet connection is working fine, Steam updates are functioning as normal.

Any help would be appreciated greatly!

:)