If your USB-C Clamp Hub for the 24-inch iMac M1 (ST-UCICHS, ST-UCICHB) is not being detected, start with the USB-C cable and which iMac you have. The USB-C Clamp Hub for the 24-inch iMac M1 was designed for the 24-inch iMac (M1, 2021) and its square back, and its short 22.5 cm cable has to be plugged into one of the iMac's USB-C ports for any of its ports to work.

How to fix detection problems with the USB-C Clamp Hub for the 24-inch iMac M1

1. Confirm you have the right iMac. This hub was built for the 24-inch iMac (M1, 2021). It will not clamp onto older iMacs with a round back because the clamping mechanism is different. For iMacs from 2017 to 2020, the Aluminum Type-C Clamp Hub Pro is the right model.
2. Plug the hub's USB-C cable firmly into one of the USB-C ports on your iMac.
3. Try the other USB-C port on your iMac.
4. Check the clamp. Turn the adjustable knob counterclockwise to open the clamp, attach the hub to the bottom right side of your iMac on the same side as the ports, then turn the knob clockwise to tighten.
5. Unplug the USB-C cable, wait a few seconds, then reconnect it.
6. Restart your iMac fully, then reconnect the hub and test again.
7. Check whether the hub appears in System Information under USB on your Mac.
8. Match your accessory to the right port. The USB-C port on this hub supports data transfer only at 2.5W (5V, 0.5A), so it does not charge devices, output video, or power another peripheral. Use it for a USB-C flash drive, external hard drive, microphone, or webcam.
9. Use the three USB-A 3.0 ports for thumb drives and peripherals. They do not support charging or CD readers, including the Apple SuperDrive.
10. Use one memory card at a time. The hub reads one card at a time, although all the other ports still work simultaneously. The SD and microSD slots recognize UHS-II cards but read and write at the highest UHS-I speeds.
11. Push the memory card fully into the slot, then check Disk Utility to see whether it appears but is unformatted.
12. Test the device you connected directly on the iMac to confirm the device itself works.