I am trying to install a game, Pillar of Eternity 2. I am unable to install OR repair but here's a detail. I was previously able to install the game on a different hard drive. I did a primary hard drive migration recently for the sake of hard drive space. This likely screwed things up.

How do I resolve this? I'm fine losing game data as well.

Uninstall then reinstall? While this shouldn't affect save data unless you explicitly choose to delete it, I recommend creating a backup beforehand.

Alternatively, you can try starting over with a fresh database:
1. Open File Explorer and enter the following in the address bar:
%AllUsersProfile%\GOG.com\Galaxy\storage\
2. While GOG Galaxy isn't running, move galaxy-2.0.db to the desktop.
3. In GOG Galaxy, click the cogwheel in the top left, and choose Add Games & Friends, then Scan Folders for GOG Games.