We are sorry to hear about the issue.
Can you please try the following steps:
Reset Lightroom preferences by holding the shift + option (Mac) or shift+alt (Windows) while launching Lightroom.
At this point, if you want to get work done, your best best is to revert to CC 2015.1.1 / 6.1.1 until Adobe sorts out all the problems: How do I roll back to Lightroom 2015.1.1 or Lightroom 6.1.1? . Today's hot fix 2015.2.1 / 6.2.1 fixes some of the problems, but certainly not all.