When I attempt to update iPhoto, a message says, "iPhoto cannot be updated because it was refunded or purchased with a different Apple ID." After hitting "OK," it then says, "There was an error in the App Store." How exactly do I update it? Any idea when that "error" in the App Store will be fixed? (I'm on a MacMini late 2012, running macOS Sierra 10.12.6)
There will be no fix. iPhoto was discontinued 6 years ago. It is no longer developed or sold. It was replaced by the more powerful (and free) Photos.app that comes with the OS. You can migrate to that app very simply:
Hold down the option (or alt) key and launch Photos. From the resulting menu select 'Choose Library' and point at your iPhoto Library. It will do the rest.
If you prefer not to use Photos there are several 3rd party apps that you can use. Which to choose depends on the kind of photographer you are and your budget.
iPhoto cannot be updated . . .
