heres how i flashed
ive had the exact same problem - its most likely because the device is not critically unlocked. For some reason it doesn`t unlock when you unlock the boot loader which can be done with `fastboot flashing unlock_critical, and in order to flash arter97 twrp, you need to make sure you flash the boot image onto boot slot a and b seperately, then flash ater97 kernel img to boot a, since there is not recovery partiticion. then go and set ur slot to a and boot while holding volume up (using the fastboot reboot recovery does not work) or reboot into recovery from bootloader and you should be in twrp. Hope this helps! also...the type c to type c is NOT meant for data transfer...only use a type a to type c!