mfdgns

I figure it out. When I tried your demo site it had these instructions:

File must contain at least 2 columns: username and email. These should be the first two columns and it should be placed in this order: username and email. Both data are required unless you use this addon to allow empty emails. If there are more columns, this plugin will manage it automatically.

Once I order the columns username and email. No errors. And I used Microsoft Excel, so that wasn’t the issue.