Data Merge not working?

Hi, I've used data merge possibly hundreds of times but now it doesn't work at all.

The palette opens. I can select "Select Data Source" and choose a file. (.csv or .txt) and then it just....doesn't do anything. Nothing loads. No errors. No nothing.

I'm completely updated both with all Adobe software and with my OS Ventura 13.2.1. I've tried saving in all versions of .csv and .txt. I've taken out the file name to be only "Book.csv" in case it's a naming issue. I've tried other files and a brand-new document. I've also waited several minutes after an attempt (in case it's a delay). I've restarted both the program and then the entire computer. I've also tried deleting my Indesign preference files on loading. Nothing ever happens when I select a Data Source. And if I go back to the menu, it still has "Select a Data Source" available.

I asked two coworkers to try it on their computers, but neither was able to do it. One was able to open a file that already had a data source, and half the time they could replace that data source with another file. The other half of the time, nothing would happen.