Purchased Fallen order through Microsoft account on PC, won't install

If you are trying to purchase Fallen Order for your PC. You can't, as it is not available for PC from the Microsoft Store. It's only Available for Xbox. For PC, you will have to install EA origin, and purchase from there instead.

If you have purchased it, and would like a refund, you can request one by filling in the online refund form

https://support.xbox.com/en-US/billing/xbox-subscriptions/digital-goods-subscriptions-refund

You would need to purchase it through the Microsoft Store app in order to play it on PC. That game is not a Play Anywhere title, so you won't be able to play it on the PC without purchasing it for the PC.

Same here. Try to download and install Star Wars Jedi: Fallen Order and Star Wars Squadrons on PC

Any games you own that are Play Anywhere can be installed from your Library on the Microsoft Store. Since Black Ops III is not available for PC through the Microsoft Store, you would have to purchase it through somewhere like Steam in order to play it on the PC.

You would have to purchase it for PC in order to play it on PC. It's not available for PC through Microsoft.