When a new Monster is first released, it won't appear in the "Possible Results" section of the Breeding Structure. This gives Handler Helpers a chance to discover the correct breeding combination on their own during the Monster's initial release period.

The Monster can still be bred during this time if you use the correct combination, even if you don't see its egg in the "Possible Results". After the discovery period ends, the new Monster will appear in the list as normal.