Ensure that Spotlight indexing is enabled on the destination volume:
- 

- Choose Apple () > System Preferences... 

- Click Spotlight. 

- Click the Search Results tab. 

- Ensure that the Applications item is checked. 

- Click the Privacy tab. 

- Make sure that the destination volume you want to install apps on is not listed. 

- Close System Preferences. Spotlight will begin indexing soon after you make any changes to Spotlight preferences. 

- Try your Mac App Store installation again.