could not start a new session on selenium webdriver

You need to pass DesiredCapabilities with marionette capability to true into FirefoxDriver as well as below :-

System.setProperty("webdriver.gecko.driver", "C:/Program Files/Mozilla Firefox/geckodriver-v0.8.0-win32/geckodriver.exe");//Now you can Initialize marionette driver to launch firefoxDesiredCapabilities capabilities = DesiredCapabilities.firefox();capabilities.setCapability("marionette", true);WebDriver driver = new FirefoxDriver(capabilities);

Edited : If unfortunately above does not work, I would suggest you to downgrade your firefox to 45 or less and use FirefoxDriver as below :-

WebDriver driver = new FirefoxDriver();

Firstly make sure all jar files added, including from /lib folder too the following snippet code would open the browser with added http link. By the way, I used win7 64bit, so keep eyes on the geckodrive path.

System.setProperty("webdriver.gecko.driver", "C:\\Users\\XYZ\\Documents\\geckodriver.exe");DesiredCapabilities capabilities = DesiredCapabilities.firefox();capabilities.setCapability("marionette", true);try {    WebDriver driver = new FirefoxDriver();    driver.navigate().to("http://google.com");} catch(Exception e) {    System.out.println(e);}