New to Firefly. I masked a subject in Photoshop, exported as PNG, & uploaded it to generate a new background. Though the prompt works, Firefly alters my subject or removes it entirely. Any tips, settings tweaks, or tutorial videos to fix this?

If you work in Firefly please post on the Firefly Forum, if you work in Photoshop (via Generative Fill, AI Assisted, …) itself could you please post screenshots (including the pertinent Panels) to illustrate the issue. 

What prompt/s did you use?