To start motion detecting operating I’ll have to try pressing some button other than the shutter because the shutter button doesn’t work.
What do you mean by "shutter button doesn't work" ? It doesn't start/stop script in CHDK, or it is generally not working on your camera?
Pressing the shutter button in alt mode is how you start scripts in CHDK. If this does not work on your camera, then either
1) There is something very wrong with the port
2) the shutter button is physically broken on your camera
#1 seems unlikely since quite a few people have reported successfully using this camera, although bugs are possible
#2 should be easy to check, since shooting normally without CHDK would also be affected
When I have time I’ll see what happens when I use the remote trigger
What remote trigger are you referring to? It's very unlikely the Canon remote trigger accessory (RS-60E3) will be seen as a shutter press by CHDK, although I'm not sure anyone has reported how it interacts with CHDK.
The CHDK USB remote (https://chdk.fandom.com/wiki/USB_Remote
) can be used to start script.
Which Canon firmware version does your camera have? You can check in the CHDK menu Miscellaneous -> Build info