The supplier may not support cancellations at search, or they may do but this is not yet implemented in iVectorOne for this supplier. The latest status by supplier can be seen in the iVectorOne Connected Suppliers, which can be found in the documentation section of this intranet.
There could still be reasons for cancellations at search to not appear despite the supplier indicating support for them, for example the product is not directly contracted by the supplier and they are aggregating from a source that doesn't support cancellations. To be totally sure, you can use the &emaillogsto parameter at search verify what the supplier is returning.
Cancellation policies should always return at prebook, however.