Problem with clipping warnings

For some reason, even when the square clipping warnings are on above the histogram in ACR, they don't change colour despite clipping in the image. However, the actual image will show red or blue depending on the clipping. Any way to get those little squares with the bounding boxes to work correctly (I tried using the U and O keys to turn them on and off but they still don't work). PS 21.2.12 and ACR 12.4.0 (cant find links to redownload those and newer versions will have to wait until my Mac is upgraded).