I cannot program the CH32L103C8T6 microcontrollers through USB bootloader. Eventhough the device is recognized successfully. The USB port works fine, because in my program I use it for data transmission. So the connections are OK.

What could be wrong?? Please help!

Hello, if you have used MRS, you can choose to update the MRS component as shown in Figure 1. After the update is completed, use MRS to export and download the WCHISPTool tool, as shown in Figure 2, and there should be no problem.

Figure1

Figure2

Thank you! It worked!