Leads not showing up during import?

Hey folks,

So, each month, we create a manual suppression list for internal purposes. It's gotten to the point this month that we upload ours. I'm doing nothing different than before, but for some reason, each time I try to upload the CSV of the email addresses, it doesn't populate in Marketo. It simply brings up an ID number with no other information.

I've already run through our "All Leads" to make sure we actually had those people in our database, and they show up there, but for some reason, they do not show up in the List I created.

Any thoughts or ideas as to why this is the case?