Why isn't my app connecting for external accounts in Shopify?

[Kore1]

We have developed an app and raised a review request to publish the app on the store. We are able to connect to this app from the stores created in our own account but it does not seem to work when App Review team tries from another account. We tried testing on the same store which App team used by asking for collaboration access for that store and it seemed to be working fine. Again our understanding for this is that as the store is in collaboration with our account it is working fine. For any other external store from another account it does not seem to work. Any suggestions for debugging this will be appreciated.