Generative Fill but not generating anything

I have an image of an ornament pattern, and I want Generative Fill to add some ribbons or cloth above it. But Generative Fill does not generate any desirable result. Instead, it was just altering the underlying image. I also tried to generate a simple white flower above the pattern, but still not generating anything. (See screenshots)

This is not the first time I have this issue. Many times already.  The Generative Fill just simply cannot generate the common object/image that I asked for, not even generating at the slightest appearance. They just alter the existing image. 

Is it a bug? or is it my images content unfamiliar for this engine at the moment? Or is it my prompt? 

Currently I am using Photoshop 25.3.1