LR Classic 7.3.1 -- brush NOT working, all else very SLOW (again!)

[HappyShotz]

I've downloaded LR Classic on my Dell PS 15 9550 laptop with dedicated Nvidia graphics card, 16 RAM, LOTS of free disc space, fast processor. The adjustment/masking brush does not work. The sliders that normally show up (such as in radial filter, which does work), do not show up and I cannot use it. I was using the 7.3.1 version, then downgraded by two versions, and adjustment brush still does not work. Not only that, whatever else I try to do is VERY SLOW. I have checked/unchecked the GPU processor button, tried installing 7.3.1 again, and it still does not work. I've tried looking thru Adobe forum but couldn't find answer to fix this.  Virus/malware protection is not preventing the program from working.

Suggestions, please on how to get this darn program working! 

[AxelMatt]

Try to reset the Lightroom preferences.