[One (M9) Q&A, Help & Troubleshooting] Flippy498:
First, it's hard to help with that little information you give. I have to assume some things so some assumptions may be wrong.

Your current state is:

Security: S-OFF? (since you already changed your CID and mentioned that you talked to beaups)

CID: ORANG001

Firmware: 1.32.401.8 or 1.40.401.8? (x.xx.401.8 is all you mentioned)

And your device doesn't boot into android and keeps rebooting if you change your CID

Well, I don't think that you converted you phone successfully to the international unbranded version since your phone doesn't accept the different CIDs.

Please read my whole answer before you start flashing since I'm describing more than one solution.

Solution using signed HTC files (inludes the stock rom):

If I were you I would convert the CID to HTC__001 and run a RUU. It's actually quite simple and afterwards your phone should boot even if you don't use your original CID. Just be aware of the fact that all your data and files are going to be deleted during this process. So backup everything that is important for you (e.g. SMS or contacts). Since you seem to be S-OFF and I don't know your current firmware version I'm going to use the 1.32.401.8 version in my instructions. It might downgrade your system but since it's a signed HTC file it won't harm your device and you can update your device using the OTA function of the stock system afterwards.

If your bootloader is unlocked you can leave it like that. There is no need to relock if you are S-OFF.

Get a SD-card that is not bigger than 32 gb and formatted to fat32 (I've always been using the formatting function of the m9 for this step).

Change your CID using

fastboot oem writecid HTC__001

in download mode.

Download this RUU.

Rename the RUU to "0PJAIMG.zip".

Copy that file into the root direction of your SD-card.

Put the card back into your phone.

Be sure that your phone is charged enough (more than 50 %; around 100 % might be better since you'll have to do some updates later).

Boot into download mode (reboot the download mode if you didn't leave it since the CID change).

Follow the instructions on the screen.

Wait some minutes.

Done.

After you followed these steps you only need to download and install the official updates via the settings menu. After that you can start flashing TWRP and SuperSu or you install a custom rom if you like.

Don't forget: 1.32.401.8 is the first officially published firmware version so your phone might get quite hot until you downloaded and installed the first update.

For being able to install later updates you either have to flash the corresponding RUU (version 1.40.401.8 if you followed the above instructions) or you need to create a backup of your untouched system:

Do not install the latest update (1.40.401.8). Only download the file.

Copy the update from /data/data/com.htc.updater/files/ to your pc.

Get the recovery from the firmware folder of that zip-file.

Format your SD-card to exfat and put it back into your phone.

Install the update.

Flash the latest TWRP version.

Boot into TWRP and mount the system as read-only. (Look at the instructions of your m9's screen.)

Create a backup on your SD-Card that contains a system image and the recovery, too.

Copy the backup to your pc and delete the "recovery.emmc.win" file. If you created md5-files you need to delete the corresponding file, too.

Copy the recovery you grabbed from the update earlier into your backup folder.

Rename the recover file to "recovery.emmc.win".

If you now want to get back to stock you simply need to copy your backup back onto your SD-card, boot into TWRP, mount the system as read-only again (mount menu) and restore the backup. TWRP will replace itself with the stock recovery then so that you can install any upcoming update. Nevertheless you need to redo this procedure every time you want to update your system.

Solution using unsigned files (you need to flash a rom afterwards):

Follow the instructions in Sneakyghosts thread.