Firefox on Android

Firstly you should install Chrome on your emulator/device. If you have done it I recommend you to change chromedriver binary at your appium node location. The related topic where workaround is described: Did not get session redirect from Chromedriver. Now you have to replace current chromedriver to actual: http://chromedriver.storage.googleapis.com/index.html?path=2.13 till new server version is released.