I'm running into an issue with a Journal Entry import, where we are specifying the Subsidiary and the Location on the import. I'm getting errors that Location 16 is not valid for subsidiary 2, but that is not even in my data set!

sometimes error “answers” are not precise; I would validate all locations are available for sub 3

In your import, also ensure that you importing a field based on either its Name or Internal ID. If location 16 is a Name/Label, but the import is looking for an ID #, it will fail. The reverse is also true. If your import is set up to find that column based on the Name, but you've provided the ID #, it will fail there too. To select one or the other, click on the pencil icon on the mapping for that field in your import, and choose between either Name or ID. I hope that helps.