M8 Failing to Unlock After Relock

Hello all,

I've been following along with instructions I've found on these forums for recovering a soft bricked HTC One M8 but I'm running into some trouble. During the process I have found that the device no longer is allowing commands that alter the lock state. The reason I'm trying to unlock the bootloader (again) is after several failed attempts at loading the RUU with very similar error messages as the one you will see below.

Phone currently has TWRP 2.7.0.2 installed but can no longer access due to locked bootloader.

Here is the result after an attempt at re-unlocking the phone (using brand new Unlock_code.bin from htcdev):

D:\HTC>fastboot flash unlock Unlock_code.bin
target reported max download size of 1826414592 bytes
sending 'unlock' (0 KB)...
OKAY [ 0.139s]
writing 'unlock'...
(bootloader) signature checking...
FAILED (remote: signature verify fail)
finished. total time: 0.149s

--getvar info---
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.29.213311491.05G
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main:
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) serialno: -removed-
(bootloader) imei: -removed-
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B13000
(bootloader) cidnum: T-MOB010
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: on
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: 205bdca3
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0

There is no mistake there. 'version-main' is absolutely missing an OS value. Even the Bootloader shows 'OS- '. Is this phone a brick now?

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