Hi, I am Dave, I will help you with this.
Many people are reporting a problem trying to switch out of S Mode for the last week, it seems to be a server side issue.
Some people have reported these steps may work to switch out of S Mode.
Open the Settings App, then go to System - Recovery.
Click the 'Reinstall Now' button in the 'Fix problems using Windows Update' section.
When that process completes, try switching out of S Mode.