HTC 820u stuck in bootloop

HTC 820u A51_DTUL PVT SHIP S-OFF
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 01.01.010_U10305041_08.01.50512
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main: 2.10.720.4
(bootloader) version-misc: PVT SHIP S-OFF
(bootloader) serialno: CC4CPYC02334
(bootloader) imei: 357585060779468
(bootloader) imei2: 357585060779476
(bootloader) meid: 00000000000000
(bootloader) product: a51_dtul
(bootloader) platform: hTCBmsm8939
(bootloader) modelid: 0PFJ10000
(bootloader) cidnum: 11111111
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: off
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: da038a09
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
(bootloader) mfg-name: 1001

i updated my mobile to 6.0, it worked fine for some day but suddenly it switched off and when i start the mobile it stuck at the HTC logo and starts again and again.
when i try to factory resset, recovery mode it didn't work.
please help me what to do.

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