Approval for a public app on Shopify store

Recently I submitted a request for approval of an app named Quickbooks POS Integration for the Shopify app store. It is an app that integrates Shopify and Quickbooks Desktop POS. The app was rejected. I would like to know what can Ido to get approval for the app. We were told that desktop apps are not allowed. Nevertheless, there are at present two apps in the app store, one named QuickBooks Desktop and another by the name QuickBooks Desktop AutomatoR, which both aim at exchanging data with Quicbooks desktop. For this purpose they must use some sort of desktop based software (Windows or otherwise). I would grately appreciate guidance in this matter.