Why can't I add variations using the ReviseFixedPriceItem or ReviseItem API?
How to revise Selling Manager Pro item variations and SKU's
Normally for an item you can
just use any of our revise item API's, and you can revise almost anything for
an item. BUT, when using Selling Manager Pro, specifically templates or
multi variations items, revising the item works a bit differently.
can still use the revise API's for certain revisions but in order to
revise SKU or variations, you must first modify the MSKU product's variations. This can be done by either the SMP
UI or by ReviseSellingManagerProduct API. After you have added the SKU or
variation information, you can then modify them within a revise item API (only
revise, not add or delete)