I have found your great app, but my Powershot doesn't switch in record mode.
How did you try to switch, using chdkptp "rec" in the CLI or "rec" button in the GUI, or using the physical controls on the camera? Only the chdkptp commands are expected to work.
If the chdkptp commands don't work:
1) What operating system are you using?
2) Does the physical camera screen go black
On linux, it's quite common for interactions with the standard software to prevent the rec command from working. This can also happen on windows if you used the filter driver instead of the INF driver.
If it's none of these things, there may be a problem with the port.