I have issues every now and then with the Mac App Store app on my computer not loading. It just sits there, not responding to my clicks and what feels like laughing in my face as I just try to update my damn apps.
I recently learned a new trick to force your updates to go through, even if the Mac App Store app is misbehaving. It requires you to go into the Terminal, but be brave and you and I can get through this.
Step 1: Open Terminal app (Applications/Utilities)
Step 2: Paste
sudo softwareupdate -i -a and press Enter
Step 3: It will prompt for your password and then perform all your pending updates.
That's it! Unlike the normal update process, it can't reboot your computer if it's needed, so heed the warning it gives you after completing the updates and restart as need be.
sudo softwareupdate -l shows all pending updates
sudo softwareupdate -d downloads, but doesn't install updates