The game wanted to update today to add Halo 3. I paused the download, but it would never resume. So I tried uninstalling (and re-installing) it, but it won’t let me. In my Windows 10 start menu the icons for MCC and MCC with mods can be seen, but according to the control panel nothing is installed. Righclick on the icons and choosing remove doesn’t do anything either. I tried re-installing, but that just gives me error code 0x80073D12. As a final solution I tried to remove the folders manually from my pc, but even that won’t work. So I can’t uninstall or re-install the game. Is there anyway to nuke the installation via PowerShell? I’m not keen on resetting my entire pc for this.
I’m getting the same exact problem, error code and everything. 
After trying again and again I get this in the start menu: Imgur: The magic of the Internet
Of course clicking the link does not do anything, can’t remove the links either. I’m really starting to hate the MS Store, where even simply installing and uninstalling an app won’t work. It’s like they’re forcing me to buy the game on Steam 
My sister is having the same problem. Has all halos downloaded but halo 3 and it wont start the download for some reason! Let me know if you guys find anything
Update for anyone. She restarted her pc and downloaded it from the microsoft store and it seems to work. You can try the whole type in “msreset” into the start menu to reset the windows store. If anyone has MAJOR issues with it a fresh install of the whole MCC would work. To do this you’d go into your hard drive and find a folder called windowsapps and delete MSIXVC within it. It would delete all associated halo files. You need admin permissions to access windows apps so theres plenty of videos on youtube on how to do that. Hope this helps!
Removing the MSICVC folder works, but it still won’t download, keep getting the 0x80073D12 error. Maybe I really should buy this on Steam.
I tried windows Key + X > run > wsreset.exe.
I was having the same problem of nothing downloading. After updating windows and trying wsreset.exe along with trying to delete the MSIXVC(which I was never able to actually delete). The game randomly started to redownload and install. I’m not sure what worked. But wsreset.exe made my computer clash at first, second try seemed to work. wsrest.exe is supposed to help with deleting unfinished downloaded games. I guess it deleted that MSI folder some how while resetting the program.
Sorry if this isn’t helpful. I hope ya can get stuff to work.