Shower Cover How Do I Remove The Drain Cover In My Shower?

How do I remove the drain cover in my shower? - shower cover

The drain cover in my shower floor flush with the floor of the shower. I tried to change, no luck. I've tried does not show up, no luck. Is there a secret I'm missing? It is made of white plastic with holes (of course) and 4-hole torn. There is only one shower and no bathtub. Ideas?

Thank you!