Import limit for Upload Customers from Spreadsheet

Summary: I'm trying to import ~3,200 customers via the simplified customer upload spreadsheet. It worked fine with 5 customers and I confirmed they imported successfully and as expected. Now I'm trying to complete my import of ~3,200 and the template no longer yields a zip file when clicking 'Generate CSV'. I've downloaded a new template, re-populated and still the same issue, no zip file. Am I running into a row limitation for the simplified template?

The behavior I'm seeing when clicking 'Generate CSV' is:

1. The typical flickering behavior onscreen when the macro is running, then
2. The flickering stops and its as if nothing happened, no error messages, nothing. This is where usually a window explorer pop-up would ask me to save my Zip file.