Originally Posted by schwags
Nevermind, it worked now. It was telling me some weird instructions, had to have it in fastboot, unplug and plug back in again without doing anything. It's booting now. Why would this happen? Maybe I just need to unlock my bootloader?
No, it has nothing to do with unlocking your bootloader. If you were using flashtool you probably didn't plug it in in the correct mode.
As for unlocking your bootloader, read the instructions on any ROM's OP. It will tell you whether it needs an unlocked bootloader or not. Sony stock based ROMs sometimes do and sometimes don't. AOSP based ROMs do need an unlocked bootloader as that is needed to flash a custom kernel. If you do want to unlock your bootloader, read up on how to root your device first without unlocking and then read up on how to back up the TA partition of your device. This partition is effectively your warranty and contains the DRM keys to all of Sony's proprietary software. If you unlock your bootloader without a backup, you lose your DRM keys and they are non retrievable. Thus, if you want to send the device off for a repair, without restoring the TA partition you cannot restore your warranty and it will be declined. Having your TA partition backed up means that if you ever need to send it off, you can restore it and this locks your bootloader and reverses any DRM key loss.
If you have any further questions please ask before doing anything. We can only help answer questions if you ask them