I have been having several issues with LR. However earlier today as I was prepapring to post the issues when I was almost ready to post I was dumped ut of this forum. LR shut down. When I tried to reboot I had a an error messsage stating I was not signed in. This is a first since I have not seen this before.
After login most issues went away. Except now Color Range Mask is greyed out and I am not able to access.
Do you have a selective adjustment tool active e.g brush gradient or radial filter? Also check you are not using a photo with an older process version - go to calibration tab or click thunderbolt icon if it appears under the histogram.