A fulfillment rule sounds harmless: aerosols ship only from the hazmat warehouse. But if one aerosol is out of stock there, Shopify returns no shipping rates and the sale dies with no error anyone can see. Fulfillment Rules checks that before the rule is live. It reads your real inventory at every location and names each product the rule would strand. Fix the stock or widen the rule, then enable it. Rules match on tags you already use. No new fields, no product edits, no theme changes.
Route multi location orders to multiple ShipStation stores...