• No shipping address found for this checkout: the order has no delivery-date line with a delivery address; it may be a pickup order.
• No Shippo sender location configured: no pickup location is flagged as the Shippo sender — set one under your delivery/pickup locations.
• No shipping rates available for this address: Shippo itself returned no rates for that address — check the recipient's state/zip, and make sure your Shippo account has at least one active carrier account connected (in your Shippo dashboard).
• Shippo: <message>: an error from Shippo itself (bad credentials, invalid address).
• Failed to connect to Shippo: a network problem; try again.

Sprwt uses the weight stored at checkout; if none was stored it falls back to the Default Meal Weight (lb) set on the Shippo integration (Integrations > Shippo), which defaults to 0.5 lb, multiplied by the number of meal items on the order (counted as at least 1).