Sky masking doesn't work - Gradient and Brush sometimes.

The sky detection mask stopped working. When I click on “sky” icon, the “detecting sky” message comes up for a split second, but nothing. Also the mask and brush selections work intermittently - I can’t tell when or why.

I re-installed lighroom, switched GPU on and off in lighroom settings.

Any help?

UPDATE: I reset all the preferences (shift + option ) on startup and that seems to have resolved it.