Why don't adjustment brushes work?

In the middle of editing a group of photos, the exposure, contrast, etc. adjustments from top section just disappeared.

Finally found the adjustment brush would show them BUT THEY NO LONGER WORK!! What in the world is going on with

Lightroom?  The forums I have read are so complicated. I had finally learned to use what i needed and now nothing~

Will have to change editing software if i can't get back to what i had.