[HTC One A9] santiago013:
I found the solucion to recover the Download mode

You need the DECRYPT RUU posted by Captain_Throwback.... that works on a linux Os i use Ubuntu with all the updates.

The stock Ruu.zip of your A9

This Ruu is extracted in ubuntu you get three files

system.img , boot.img and a folder named Firmware----We just need some .img firmware files

On windows put the files on the folder HTC Sync: aboot_signed, cota, hosd_signed, rpm-8952-1 (i thinks tha may vary), recovey_signed, dsp, keymaster

flash on bootloader via fastboot. if you want to help others to find the exact file put the command: adb reboot download

if not works reenter to bootloader mode and flash de next file.

i flash all and forgot do that.

I hope excuse the English

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot erase system

htc_fastboot v3.0.9.2 (2015-05-29)

******** Did you mean to fastboot format this partition?

erasing 'system'...

OKAY [ 2.284s]

finished. total time: 2.284s

htc_fastboot finished. total time: 101.203s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot erase boot

htc_fastboot v3.0.9.2 (2015-05-29)

erasing 'boot'...

OKAY [ 0.078s]

finished. total time: 0.094s

htc_fastboot finished. total time: 0.438s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot erase recovery

htc_fastboot v3.0.9.2 (2015-05-29)

erasing 'recovery'...

OKAY [ 0.078s]

finished. total time: 0.078s

htc_fastboot finished. total time: 0.437s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash aboot aboot_signed.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'aboot' (776 KB)...

OKAY [ 0.156s]

writing 'aboot'...

OKAY [ 0.031s]

finished. total time: 0.188s

htc_fastboot finished. total time: 0.766s

abd reboot download

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash recovery recovery_signed.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'recovery' (47317 KB)...

OKAY [ 7.880s]

writing 'recovery'...

OKAY [ 1.124s]

finished. total time: 9.004s

htc_fastboot finished. total time: 10.390s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash hosd hosd_signed.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'hosd' (48965 KB)...

OKAY [ 8.100s]

writing 'hosd'...

OKAY [ 1.172s]

finished. total time: 9.272s

htc_fastboot finished. total time: 9.725s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash rpm rpm-8952-1.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'rpm' (162 KB)...

OKAY [ 0.031s]

writing 'rpm'...

OKAY [ 0.031s]

finished. total time: 0.062s

htc_fastboot finished. total time: 0.748s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash cota cota.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'cota' (61440 KB)...

OKAY [ 10.167s]

writing 'cota'...

OKAY [ 1.429s]

finished. total time: 11.596s

htc_fastboot finished. total time: 13.112s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash dsp dsp.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'dsp' (16384 KB)...

OKAY [ 2.740s]

writing 'dsp'...

OKAY [ 0.393s]

finished. total time: 3.133s

htc_fastboot finished. total time: 4.133s

C:\Program Files (x86)\HTC\HTC Sync Manager\HTC Sync>fastboot flash keymaster keymaster.img

htc_fastboot v3.0.9.2 (2015-05-29)

target reported max download size of 536870912 bytes

sending 'keymaster' (147 KB)...

OKAY [ 0.031s]

writing 'keymaster'...

OKAY [ 0.031s]

finished. total time: 0.062s

htc_fastboot finished. total time: 0.797s

When yoy find the Download Mode .img

I think it would be good flash the recovery_signed to format data, then go back to download mode. Now you continue testing roms