How goods travelling to the warehouse are handled: the connector announces incoming Odoo receipts to the 3PL as ASNs (Advance Shipping Notices) so the warehouse expects them, then pulls the warehouse's GRN (Goods Received Note) back so Odoo's receipt shows what was actually counted in.
ASN/GRN and supplier sync are part of LataSys 3PL Connector: Inbound, a companion app installed alongside the core connector. Installing it reveals the inbound menus, buttons and settings; without it the flows stay off and inbound receipts are managed directly in Odoo Inventory as before. Existing installations upgrading from an earlier version get the app installed automatically, so nothing they were using changes.
With Send ASNs on (Sync Settings tab), the scheduler sweeps the open incoming transfers of every mapped warehouse and creates one ASN per receipt, announcing it to the 3PL with the purchase order's reference where there is one (else the receipt's name). ASNs live under Operations and on the receipt's 3PL Connector tab; each one can also be announced by hand with Announce to 3PL.
Exclude Return Receipts from ASNs (Settings reference) keeps the sweep away from receipts created by Odoo's return wizard for customer returns - those goods already reach the warehouse through the returns flow, and announcing them a second time as inbound deliveries confuses their booking-in. Turn it on when you run both flows.
Cancel at 3PL on an announced ASN withdraws the announcement at the warehouse - the goods are no longer coming, or the announcement was wrong. The Odoo receipt is untouched; the ASN returns to To Send so it can be corrected and re-announced. The button only appears for providers that support cancelling an ASN via API, and a 3PL refusal (for example, goods already booked in) is shown with the exact reason.