I've tried both Auto and P shooting mode.
Yes, I built the remote per the instructions in the link I sent. It connects to the camera's mini-USB port and actually snaps a photo when I press the button, so that part of it seems to work.
The canon firmware version that Stick reports is: Canon PowerShot ELPH 100 HS - 101c Stable CHDK
I tried normal mode->same result. No photo on SD card.
The SD card is locked. So, I assume it's "SD Override" that allows the picture to be saved on the locked SD. Perhaps SD override is not working right?