Omeka API Import Status: Error

I’m trying to transfer my Omeka Classic install from one server to another, which I’ve done in the past, but this time, it’s not working. The API is turned on, the API key appears to be functional, and the URL appears to be correct. I click “Submit” and the status says “error” with no other information. It continues to import, eventually saying “status: complete,” and all my items are imported, but none of them have any files.

(I have the files - it’s about 40gb, I can just move them to the correct folder, but that won’t tell the SQL database about them.)

Any ideas about what could be going wrong?