Good afternoon carmen tam,
Welcome to the Apple Support Communities!
I understand you are seeing a red X on your Apple Watch series 3. That indicates that your Apple Watch has lost connection with your iPhone. The resource below explains how to reestablish the connection. I've highlighted some key information here for you. Click on the links for complete details.
About Bluetooth, Wi-Fi, and cellular on your Apple Watch
Check the connection between your devices
There are two ways to check the connection between your Apple Watch and iPhone:
- If you see or on the watch face, you don't have a connection.
- Swipe up on the watch face to open Control Center, which shows if your devices are connected. You can also tap . If connected, your iPhone should make a "ping" sound.
Enjoy your day!