First make sure that you’re using the latest Google Chrome version available. You can easily update the browser via the settings menu on the upper right of your browser window, and selecting "About Chrome".
If you already have the latest version the problem may be that your Chrome profile is defective. To test this, please add a new Chrome user profile to your browser. You can easily do this in your browser settings - either go to your settings directly or copy/paste this into your browser: chrome://settings/
Scroll down to “People” and click on "Add new User", this will open a new window with the new Chrome user. Now please try to add ZenMate, via the Chrome Store, to this new browser user profile.
If it still does not work you may need to reinstall your Chrome browser all together.
Please note that this is a problem with the Chrome browser itself, it is not caused by ZenMate.