My Base for XIAO expansion board also became defective after programming with the Segger J-Link debugger. I only used USB-C on the XIAO MG24. The debugger was not supplying power. Otherwise, the error was the same as described by sidcha. The XIAO MG24 was working fine afterward, and after soldering the connections to the SWD interface, it was programmable again with Simplicity. Unfortunately, I only found the post afterward.