After unsuccessfully attempting to convert my AT&T-branded HTC M8 to the Developer Edition (using the nandroid method), I ended up restoring to stock using the official RUU. I'm experiencing two mildly annoying issues that I hope someone can help me out with. The first one is not being able to change the CID back to AT&T's (CWS-001). I tried it a few times and fastboot returns the "invalid cid" error each time. I was, however, able to change the CID to SuperCID (11111111) without any problems.
The second issue is that I am still unable to boot into stock recovery and get the red triangle with an exclamation mark when I try to do so. I am running the latest firmware version (1.58.502.1), but was unable to find the recovery for that version, so I flashed 1.12.XXX.X. I have a feeling that this may be what's causing the problem.
I'd like to restore completely to stock. Can someone point me in the right direction?