We are using the app proxy to make requests to our back end, shopify passes along the logged in customer id to our back end so we can figure out who they are. The problem we are seeing is that if a user's shopify session sits for a few days (like over the weekend) and they come back to the shopify store that they are logged into (and they are still logged in as they can click on their account and see their orders), the app proxy stops passing along the customer id until that user signs out and signs back in again. Why is this happening?
