Cannot uninstall Halo: The Master Chief Collection

I have the Halo: The Master Chief Collection installed on my PC. It used to work fine but when I tried to launch it today it gave an error: Something to do with being offline. I found the game in the Microsoft Store and clicked the repair button. After doing
this Windows no longer sees the game files. I cannot find the game in search or see it in Add or Remove Programs despite it still taking up over 60 GB of my drive.

In the Microsoft Store there is an update pending for the Master Chief Collection but it will not start downloading. The Store gives me the option to reinstall the game but if I try it gives this error "Before you can install this add-on, you need to install
the app or game that it works with. Code: 0x80073D12"

I have updated Windows, updated all apps in the Store (apart from the MCC update that won't download) cleared the store cache, reinstalled the store. The outcome is unchanged.

Does anyone know how I can get my 60+ GB of drive space back short of formatting and completely reinstalling Windows?

:)