Thank you for your reply. The red area in your screenshot is not part of the layout, so it is not possible that is showing on your player. The black area in the preview window is empty space outside of your layout. The grey area is the layout, 1920 wide by 359 high. You need to add all of your media items to that grey area for them to display on your player. Please also note that you may need to set the player window size to match this resolution, to ensure your layout fits correctly.
For example, lets say I create a 1920x359 layout:
All layouts have a single region that fits the full layout by default. I will keep this default region and add some text to it:
You can see that the text fills the grey area, as this is the layout area, not the black area.
If I connect a 1920x359 screen to my device running my player, I can set the player window dimensions to match the layout resolution:
Once the player has received those settings and been restarted to apply those changes, I can schedule that layout to the player and it will fit the full screen. Only the area in the layout designer that is grey will be rendered, anything outside of that grey area will not appear.