Try these:
a. Open Terminal and run this command:
open $TMPDIR/../C
b. Locate and delete the folder called "com.apple.appstore"
c. Now, go to this folder and delete everything:
/Library/Updates/
d. Once done removing all these stuff, restart your Mac and empty the trash. Then run this command using Terminal:
defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock
This should solve your issue. :)