As above, all three shields are blocked by my MacBook Pro running OSX 10.13.4. When I click on the “Allow” button in Preferences/Security & Privacy, the button blinks but nothing happens. How can I make my MacBook Pro allow Avast to turn on this real-time protection?
unfortunately, the ALLOW button functionality is somehow unreliable. try to open/close the Security&Privacy dialog several times and click it. It’s happening randomly. I was able to click it after a few attempts. looks like some Apple/macosx issue 
Here is the fix.
Try clicking the allow button after closing chrome.
Guess that Mac and Google don’t play nice together 