Hi LE, are you using the free Store Exporter Plugin or Store Exporter Deluxe? What version of our Plugin are you using and is this for WooCommerce?
This is likely a configuration issue with your server, see https://wordpress.org/support/topic/fatal-error-ob_start-cannot-use-output-buffering?replies=8 as a related issue. If you can provide more information requested above I can help further 🙂
