EMR dyanmodb export failed because of table capacity set to on-demand

I'd contact AWS support to confirm, but I was told the EMR DynamoDB connector does not formally support tables using on-demand provisioning yet. So, more than likely you need to switch the table back to provisioned capacity as a workaround.

Edit: As of 23 January 2019, the EMR connector for DynamoDB supports tables set to on-demand billing.