If you're unable to swipe the screen of the Xiaomi Watch S4, try the following steps to resolve the issue:
1. First, check if the battery level is too low. A drained battery can cause screen responsiveness issues. If the battery is low, connect the watch to the charger and let it charge;
2. If the screen still isn't responsive, press the rotating crown (upper button) to return to the watch face. If swiping still doesn't work, perform a forced restart by holding the power button for 12 seconds;
3. If the issue persists, try performing a factory reset. Hold the power button (lower button) for 3 seconds, select [Factory reset] in the system options, and rebind the watch to your phone.
If none of these solutions work, consider contacting the local after-sales service center for further assistance.