Can't Unlock Bootloader , Can't enable OEM unlocking option in settings, Help

I wanted to unroot my device to send it back for repair ( screen shattered).
I made a backup, flashed this stock recovery(http://ift.tt/2aAvGbR) locked my bootloader, wanted to enter stock recovery to sideload stock rom, but fails .

When i enter recovery mode, Oneplus logo flashes 3 times then everything turns black except notification light turns on.

Now I want to try to unlock the bootloader again so I can flash another stock recovery. But it says : (remote: oem unlock is not allowed )

I know that i have to enable it in settings, but I cant boot my phone to the rom / software. So now i am stuck, I can't enter recovery mode because I messed up, I flashed a "wrong" stock recovery before locking bootloader.
Any suggestions?
Please help me with this problem.

Thanks in advance

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