First person - camera not on floor in play mode

Hello - starting my basic BSP geometry on a new default level, with first person starter content. I added a basic floor, making sure it was snapped to grid. I put the “shooter” camera on the floor, adjusting it so I could see where I wanted it via the preview window in the bottom corner.

However, when I try the Play mode, the camera appears above the ground, and I can’t position it onto my ground floor. What am I missing?

Thanks for the help!