Declined lines are freed up and you can re-assign them to another supplier; orders only start once every slice is approved.
The Split Award Board tracks each supplier's decision separately: Pending, Approved, Declined. When a supplier declines their slice, that slice's lines drop into the Re-source list at the top of the board, with the supplier's reason shown next to the line if they gave one.
The Re-assign button next to a line lists the other suppliers who quoted it, with their price — including offers submitted after you built the split, and excluding the supplier who declined. Pick one and the line moves to them, with their decision back to Pending. If no other eligible supplier quoted that line, the list comes up empty.
Approvals already given by the other suppliers stay in place, so you never rebuild the split from scratch. Once every slice is approved, the board unlocks Start orders — nothing is ordered until you click it. While an approval is missing, the board reads "Waiting on all suppliers to approve before starting orders."
The Split Award Board and the multi-order flow are a higher-plan feature.
Also asked as: What if a supplier doesn't approve their slice? · Can I give a declined line to a different supplier? · A supplier declined — do the orders still go out? · What happens to lines a supplier turned down?