Your app-user(s) must sign in while they have Internet to make sure the service loads. Also, they should select the assigned service and scan a demo barcode to ensure that the scan engine is active. For instance, the barcode can be the one you provide as part of your instructions. Also, it can be any barcode they can find.
Thereafter, the app-user will not have to sign in to the app with connectivity for up to 5-days. However, if you change any attributes for your services or make database changes, they will need the Internet.