ChromeDriver error "unknown error: cannot get automation extension"

You need the latest version of chromedriver.exe. https://sites.google.com/a/chromium.org/chromedriver/downloads

This is needed for chromedriver version 57+

I was having this same issue. Once I updated the chromedriver version everything worked again.

This could probably because the environment where you are running the tests is blocking all the third party extensions in chrome browser. Give it a try with disabling the extensions.

something like below:

ChromeOptions o = new ChromeOptions();
o.addArguments("disable-extensions");
o.addArguments("--start-maximized");
WebDriver driver = new ChromeDriver(o);

Suddenly got this error -> Additional information: unknown error: cannot get automation extension from unknown error: page could not be found: chrome-extension..

This issue exists even when using ChromeDriver 2.29
What solved it though was removing this line.

driver.Manage().Window.Size = new Size(1024, 768);

A quick fix but really not the one I've been looking for. Would be great to still use the sizing mechanism.