Are you sure you have the correct access rights for the entity the microflow is returning? It could be that the microflow returns an object the user has no access rights for, in that case the object is not returned.
An easy way to check this, is to enable 'apply entity access’ in the microflow. If you can stll see the objects to be returned in the debugger, you know you have the correct access rights. If you don't see the object in the microflow debuger, you do not have the access righs.