[Existing Game Files] How to use?

@aFatLilGoat That message typically indicates you either do not own it, and another account downloaded it, or the game/app is not installed on the same drives so it doesn't recognize the game linked to the account.

I see that you have two drives, so try the following:

• EA App's Cache (Top Left Menu > Help > App Recovery)
• EA App - Repair (My Collection > Tile Dots > Repair)

relaunch the App, on the left, you should see Home - Browse - Library

If you do not, close down the app and try the following

• Press the Windows key + R, go into the file explorer, type in %temp%, and hit Enter
• Delete everything it allows you to delete.
• Then in the same run box, type, %temp%, and hit Enter
• Delete everything in the Origin folder except the local content.
• Reboot the PC

@EA_ShepardWhere is "my collection" ?

Nobody has ever logged into EA on this machine other than my account, before or after the reimage. And I do own the game, it was downloaded via the EA app before it was reimaged from my account.

Also, what do you mean by local content in the origin folder? I only see an Origin folder in the appdata/Local/Origin
So delete nothing in that folder?

But it was never an issue for me not being able to see home/browser/library, so I don't think that fix is relevant. I can see those buttons, my problem is that I cannot manually launch the already installed game or tell origin where to get my game files. 

@aFatLilGoat This message "you don't have access; This title may have been downloaded to your device by another user who owns the game. Log in to a different account or restart the app to try again" only happens for a handful of reasons. I get this error if I log in from work to personal or vice versa and try to launch a game one doesn't own.

• You don't own the game: You had EA Play and the sub expired
• Someone else owns it
• You downloaded a trial/beta/test and no longer have access to the game
• There is content for the game you do not "own" This does not apply to every game

As for these steps, Origin shouldn't be in there, I apologize for that.

• Press the Windows key + R, go into the file explorer, type in %temp%, and hit Enter
• Delete everything it allows you to delete.
• Reboot the PC

Some of this won't let you because you are running those programs. After that, you can uninstall the app and the game and reinstall both to the same drive if you have more than one drive.

Once everything is removed, you can repair  the game, or you can reinstall the game on the EA account you use from your library section of the launcher.

As already mentioned, I do own the game. It was downloaded from my account via the EA app, before I reinstalled windows. So nothing that I do not own is downloaded. 

I'm aware that if I redownload the entire game that is already downloaded it will then work. The question is how do I avoid doing that because this isn't the only game that is affected. 

I have little over 1tb of games that would have to be redownloaded if the EA app does not have this basic QOL feature. Even origin was capable of navigating to pre-existing game files, can the EA app not do that? I see nowhere in the settings for this even being a function. 

@aFatLilGoat  No, the EA App doesn't have Origin's Locate Game feature, at least not now.  What you can try though is setting the App to download to the same location where a given game is already installed.  When I've tried this, the App has usually just verified the existing files and finalized the install, although I did see it redownload a couple of Sims 4 packs in their entirety.

The other cause of the "you don't have access" error is a temporary hiccup with the App, which can usually be cleared up with an App Recovery:

https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/

I'm not saying this will help here—reinstalling Windows means you wiped the registry entries that the App needs to verify your ownership, which is the cause of your current issue.  I'm just mentioning it in case you run into the problem again down the line.