HTC U Ultra repair imei fail

Hi,can not repair imei

1. Checking phone connectivity...
Warning! Your phone does not see the XTC 2 Clip, please try to reconnect it, and then reboot to download/fastboot mode. In case of failure again, check your flex cable for damage.
Phone connection confirmed!
HTC KEY CARD VERSION: 7
2. Checking Server connectivity...
Server connection confirmed!
3. Checking PowerAdapter connectivity...
Process started
PowerAdapter connected, processing request to adapter...
Starting operation...
Sending oem writeimei 35516869653897
... (bootloader) [ERR] Command error !!!
OKAY
Execution time is 2(ms)
Operation completed!
Releasing adapter.
Request completed