820n Flash Problem
 

Starting flash process...
target rom version: 3.17.401.3
found large-zip header, file count: 8
processing file 1/8...
sending 'zip' (49306 KB)...
OKAY [ 2.811s]
writing 'zip'...
(bootloader) adopting the signature contained in this image...
(bootloader) signature checking...
(bootloader) rom parsing start ...
(bootloader) rom parsing finish ...
Error: Not allowed. Probably phone is not in RUU mode. Please switch to RUU mode and try again
finished. total time: 7.330s
Flash process completed.
Flash not successfull, reboot will not be done

Hello,

Are you trying to flash in RUU mode?

The phone is always restarting when I click the RUU button

Then I can recommend you 2 options:

1. Flash partial flash first (search for "partial" on support).
OR
2. Use SD flashing.

Copy the flash file to SD card and do partial upgrade flashing. After that Device will come in RUU Mode.