One M8 won't OTA update on stock

I returned my M8 International Unlocked Dual SIM Version through a nandroid backup and then flashed one of the recoveries I found online but my phone won't update through OTA. I then tried restoring different backups. Some of which worked and some didn't even boot.
I finally came to the conclusion that it was because of the HBOOT version and maybe the version-main.
I want to know:
1- Understand version-main.
2- How can I know which nandroid backup is right for me. (and if possible point me to the right ones for me).

I searched quite some time but couldn't turn up with a complete answer. Forgive me if I missed something.

Code:

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(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.24.30336021.13G
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main: 4.30.401.15
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) serialno: HT474WM05260
(bootloader) imei: 352272060737805
(bootloader) imei2: 352272060737813
(bootloader) meid: 00000000000000
(bootloader) product: m8_dugl
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B64000
(bootloader) cidnum: HTC__J15
(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: 49d38c68
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0

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