When you are using the WS1 Pro device and connect the TH30S-B external probe, you usually go to the Settings page to enable the RS485 button first. Please note, you only need to enable the RS485 button if there is only one probe is connected. If you turned on other buttons, such as external probe, RS485 S (for soil probe), the data on the device screen will flash automatically.
Therefore, please remember to enable just the corresponding button for the probe you're using.
Tips: For TH30S-B and Soil probe, they can only be connected to the bottom USB port (USB2) on WS1 Pro device. WS1 device doesn't support them.