I met this problem mate.
You just go to this link: https://github.com/Seeed-Studio/ArduinoCore-samd/tree/master/bootloaders/XIAOM0
download the XIAO bin file then, Use SWD to burn the firmware into XIAO, it will be work again.
How to unbrick a dead xiao using raspberry pi [ GUIDE ][openocd]
Also, you can buy a Jlink to burn the firmware into XIAO.