Import says Internal ID isn't there, but ... it is?

Hello. I need to mass update the posting period for hundreds of vendor bills today, pushing them back into 2024.

Please see the screenshot below. I think I'm using the right import and mapping it correctly, but I get an error. What am I doing wrong here?

https://preview.redd.it/vl1np1fcuxfe1.png?width=592&format=png&auto=webp&s=cfc008ceeaa223f736bae1e9d4b8687ca1df8662