If you power on your Samsung monitor and once the monitor boots up you have the screen below please follow these steps to change the source back to Web Browser to bring the Spindle Display on-screen.

Please note you will need your Samsung Remote to complete these tasks

1. Press the Source button
2. Navigate to Web Browser using the left arrow on the remote
3. Press Enter on the Source to launch the Spindle Display

Should the display open with the URL and tab screen open please follow the steps in the article  Spindle Display has URL Bar Stuck on Display