Hi I just test HID and it’s working. The problem is with your script, you’re sending bytes in the wrong order. This script works:
import pyb, time
kb = pyb.USB_HID()
buf = bytearray(8)
while(True):# Sending T
# key down
buf[0] = 0x02 # LEFT_SHIFT
buf[2] = 0x17 # keycode for 't/T'
kb.send(buf)
time.sleep(10)
# key up
buf[0] = 0x00
buf[2] = 0x00
kb.send(buf)
time.sleep(1000)
Please read MicroPython’s tutorial first to understand how HID works: