Toggle per User Guide is to switch a locomotive that has been running in Bluetooth mode to DC mode.
DC mode is not compatible with all power packs. What brand and model power pack are you using?
Also,
When operating the throttle in DC mode, you may notice a slight delay when starting your train with the throttle in the OFF position. The board in the loco doesn’t activate until your throttle reaches approximately 15% throttle power. To avoid this delay, only bring your throttle down to the 15% mark when stopping your train. This will allow the board to remain powered up, and avoid any initial lag.