[Q] HTC One M8 (HK)- Help flashing Lollipop topic

Hello all, I have searched for more than a couple hours and just seem to be getting nowhere. Here's the deal: I have an HTC One M8 with TWRP, root, an unlocked bootloader and S-ON. I want to install Lollipop, but can't take the OTA.

I know a little bit about what I'm doing, I tried to flash a rooted stock ROM but it didn't take. I wiped all directories but the internal storage. Also wiped the Dalvik, `but I could not get the update to take. I tried a few other things but out of fear of bricking my phone I wasn't very adventurous. I flashed the backup I made beforehand and it worked fine.

I think I have the wrong file...? Could my S-ON be the problem?

Sprint HTC One M8 (HK edition)
Android: v4.4.4
Sense: v6.0
Kernel: 3.4.0
Baseband: v1.08.20.0916
Build:3.31.654.2

All I want to do is flash lollipop. Will I have to lock the bootloader and go back to stock recovery to do it? Can I use adb sideload to install it via adb?

Thank you for your time.