[Q] Can't boot into recovery after flashing TWRP 2.8.4.0 topic

Hi everyone, so this is my first post here on Xda, heard a lot of good things though:)

Anyways, I just re-rooted my HTC One M8 at&t model for the second time, I have rooted before, but had some issues so I decided to unroot and relock it, that is until today, when android 5 came out for the developer edition I decided I would try to convert mine so I could install the official ota.

So I unlocked my bootloader and flashed

./fastboot flash recovery openrecovery-twrp-2.8.4.0-m8.IMG

Said it wrote it successfully, so I tried to boot into recovery to flash super su.

When I tried however, it just sat and hung at the "entering recovery" screen.

I held down the power and volume up to get back to my home screen and retried after booting back into the bootloader.

Same thing. Not sure what I did wrong. I installed TWRP for gsm models (like I should have, right?).

Is it possible that somehow the old version of TWRP from my previous rooting experience is creating conflict with the one I just flashed? I'm really new to all this, so thanks for putting up with my uneducated self:)

Any ideas?

Thanks in advance!-Z