@Gregory Jones Yeah, it looks like my issues lie elsewhere. I'm trying to assign matrix children to a parent in one import, using the Name of the parent I established in the previous row as the key, but it's saying the parent reference key is invalid. It works when I use Internal ID, but then I have to do all the parents first, followed by the children to establish that Internal ID. It's not a huge amount of extra work but it is an extra step.

fwiw i always do separate imports for parents and children