If you are using Lightroom 6, please reset Lightroom Preferences back to default.
Press the shift + alt keys. In the resulting Reset Preferences dialog box, indicate you want to reset your preferences.
Let us know if that helps.
Dear Mohit, thanks for your suggestion. I am using LR CC 2015.3 Release, but the slideshow module never worked. I tried resetting the preferences but I couldn't follow your instructions.
BY pressing the shift + Alt keys I get the select catalog window. Thx