When a test fails, you will get an indication next to each step that fails. Usually you should look at the first failed step to figure out why the test failed. There are a number of tools that will help you troubleshoot your failed step:
Screenshot - available when clicking on the failed indication icon on the top right of the each step.
Video - Available by clicking on the "Play" icon on the "Results" tab.
Logs - Device and Appium logs are available underneath the screenshot
All of these should help you troubleshoot what happened while the test was executed.