I am currently rooted, and have CWM installed. The device is obviously Bootloader unlock. What I was able to find is that it possibly could be a issue that it is bootloader unlocked as some posts suggest to have you bootloader locked to install RUU, but that is obviosely not a posibility with the dev ed.
So what am I doing wrong, or what is the issue. I have confirmed that I was using the correct RUU.
Ok, I figured out how to avoid the RUU 155 error. It seems that HTC for some dumb reason, although for a unlocked developer edition, we still have to lock the bootloader to utilize the RUU. Here are the steps I have done.
Although it is straight forward and easy to do, issues could always arise. I do not take any responsibility if things go wrong. Educate yourself first before attempting anything. If you do not know what you are doing, then don't do it.
Make sure you have the latest HTC Drivers. You can use hasoon2000 HTC All-In-One Toolkit to complete that. That can be found at HTC One All-In-One Toolkit
Get the appropriate RUU from HTC Dev
1. Lock your bootloader through by booting into hoot and then going into fastboot and issuing the command fasboot oem lock.
2. Once locked, reboot your system.
3. Open RUU and follow onscreen instructions.
Notice, this will delete all of the files on the system so do this on your own cognition
4. Let the RUU do its thing. If you get an error during the process, such as 152, simply try again. I had it happen once. The phone was stuck on the black HTC screen with four triangles with exclamation points in each corner. If this happens you will not be able to reboot your phone. Simply relaunch RUU and it should reinstall it. If you get error 155 again, then you have not re-locked your bootloader.
3.Once you have successfully reinstalled the rom, you have to register with the HTC Dev to re-unlock your bootloader if that is what you want. The easiest to do this I found was by using the HTC One All-In-One Toolkit. It is a great tool and will help you with majority of things that I have mentioned above, including locking your bootloader. Follow the steps on the toolkit and you'll be all set. The Toolkit can be found here HTC One All-In-One Toolkit
If you found this helpful, click thanks. Also hit thanks to hasoon2000 for creating the toolkit.