My Adjustment brush has stopped working

[Flexigav]

I use ACR quite a bit, but now the Adjustment Brush has stopped working. I can set the starting point but dragging the brush over an area shows no adjustment happening—regardless of the adjustment option. When I check all my adjustment points, none show they cover any area, all I see is the entry point marker. The gradent adjustment still works. I read through some other posts with this problem and an update seemed to be the solution. I updated my ACR so now are running version 12.4 for Mac. Unfortunately my adjustment brush still does not work. Anybody know of a solution? 

[Chuck Uebele · Accepted solution]

Try resetting the preferences in Camera Raw: 

https://m.youtube.com/watch?v=4Y7AzupMPl0

[Flexigav]

Thanks Chuck Uebele, that worked. I try my best to stop programs from making changes in the background but it still beats me how these things change. All my updates are set to manual so I have control of when they happen so I can backup first but still application programs change in ways detrimental to my use—without warning. It is hard to imagine tomorrows computing.

[Chuck Uebele]

This just get corrupted sometimes.