Hi anson , first off thank you for the follow up, you guys at Seeed are great!
It was an issue I was using an older lib of the Grove 10DOF, compiling is no problem now but an unusual issue.
Arduino SAMD Boards is 1.8.8 but my board selection is : Seed SAMD(32bit ARM…) > Seeeduino XIAO
Nothing prints to serial, could you confirm if you are getting an output?
I tried changing the Serial port number in the sketch and it’s not a problem with the XIAO, it was fine with other sketches correctly printing output.