Error returned: 'OLE DB or ODBC error: [Expression Error] The column 'X' of the table not found...'

Posting this in case it helps someone else in a similar situation. I had this error when loading a group of json files from a SharePoint folder. The issue turned out to be that one of my 50+ files was empty, so there indeed was no column, but just in that one file. Troubleshooting that was a real head-scratcher. I ended up creating another folder and copying just a few of the files into it and loading that worked perfectly. So I had to narrow it down to the bad file essentially by process of elimination. In hindsight, I could have also looked at the file sizes to figure out one was empty.