help for remove pattern sm-t715y

hi i want remove usre pattern tablet tab s2(sm-t715y) with bst dongle but error occured : Unlock … failed to connect device
Prepare environment … Device do not have ADB interface, turn on device USB DEBUG and connect with usb cable,then re-scan device
Need reboot device to normal
Time used : 1 min 17 s

plz help me