Can you try to reset the XIAO before uploading the sketch, it might be stuck in the HID Mode!
To Reset
- Connect the Seeeduino XIAO to your computer.
- Use tweezers or short lines to short the RST pins in the diagram twice.
- The orange LED lights flicker on and light up.
At this point, the chip enters Bootloader mode and the burn port appears again. Because the samd21 chip has two partitions, one is the Bootloader and the other is the user program. The product will burn a bootloader code in the system memory when it leaves the factory. We can switch modes with a quick reset.
Source: Getting Started with Seeed Studio XIAO SAMD21 | Seeed Studio Wiki