If the free credit report you got from the source says the debt is paid, then what CreditKarma says doesn't mean anything. Understand what CreditKarma does, they exist to sell you products and services (hence, why it is free).
It can take up to 60 days for an item to be removed from a credit report, or at least to show paid. Please understand that simply paying a debt does not cause it to be removed. More likely, it will show as paid, but remain on your report for 7 years from the date you paid it. The only way it will be removed is if you negotiated that with the collector.