How long did you hold down the power button? Your phone should power itself off when you hold it down long enough. It may take several seconds.
When Odin shows you that 'Pass' flag, you want to initiate a manually induced shutdown. You need to force your phone to turn off, you don't want to allow your phone any time to run through its normal shut down procedure (timing is important) -- that cursed recovery-from-boot.p script will run, replacing the TWRP Recovery you just implemented with the original Recovery.