[One (M9) Android Development] Sneakyghost:
My apologies I misunderstood. I understood you tried to flash the firmware with TWRP.

Good to know it can be flashed through a locked bootloader when S-OFF. Thanks.

__________________________________________________________________________________

Further information for newcomers (OP will be updated accordingly soon)

Here is a complete RUU flash log for your reference if you want to compare to your own flash processes:

After a fair share of dicking around yesterday and today with ever so failing ARUWizard.exe and fastboot.exe flashes and failing SDCard method flashes (yes every single method with any variation you could think of), I finally had an idea why those would fail but others could easily flash their RUU.zips on the M9.

First, we have not gotten an ARUWizard yet. This is very unusual. People even searched the HTC servers by guessing their way around filenames and found lots of RUU zips but no packaged RUU.exe.

Secondly, different fastboot variants would throw different errors. Some pointing out wrong zip size, some (on mac!) report sparse image errors and signature errors. This eventually lead to my slow brain having a short bright moment. 2GB zips! Wasn't there something with 64bit architecture vs 32bit architecture and certain address-space limitations? I thought the fastboot.exe was probably old, 32bit and not capable to handle 2+GB files. Well. When I asked around it appeared that those RUU.zips which were slightly below 2GB would flash and those that were bigger, not. I don't have hard evidence on this but it did make some sense in my humble potato brain. So. Old Fastboot no go.

Third, I kept trying to flash the RUU.zip with my 64GB SDXC. SDXC is per definition to be formatted in exFAT, nothing else. Neither the M8 nor the M9 can read an FAT32 formatted SDXC. Therefore, i packed the 0PJAIMG.zip onto my 64 and thought screw dat. It MUST be working with large exFAT cards too. Why not. But in fact, it didn't. So i went and threw another 20 bucks out the window and got myself some old 16GB SDHC with FAT32. That worked instantly. First time the flash succeeded.

So, now I knew the zip was good and Aboot was able to handle it too. Just Fastboot or ARUWizard or my Cable or my PC remained.

Lucky me, I got some updated htc_fastboot from someone to try last night and surprisingly, it was capable to read the zip and flash it until it reached the last internal Part 7 (RUU zips are packed with a bunch of sub-zips, usually 7 on the M9), then it failed and my phone was left in nirvana with nowhere to go to. Well. It only failed to flash dzata and boot.img luckily, which are the files in that last part. So I was able to reboot into bootloader and restore some backup until I could buy an SDCard today. Well, anyhow. The updated htc_fastboot was no good either then...

Today i asked around and found someone who knew someone who knew someone who gave him some very much updated htc_fastboot.

That works. RUU flashing with Fastboot or ARUWizard can now be considered working thanks to "that guy" who managed to sneak that out of HTC's protecting hands. Not naming [MENTION=494185]LlabTooFeR[/MENTION] here. No. But who else could possibly get us that. Thank you, mate! So Helpful!

I will update my "Android Batch Tool" on the first page once I know i can share that fastboot.

Until then, people, do not despair. The issues you face are normal and there is a solution coming.

Batch Tool in Post #4 updated with new, working fastboot and adb.