By default, the B4A IDE filters out most log events (in the "Logs" list) happening in the device and just displays the events associated with your app.
So, to get more clues on what is causing the crash when your app starts, try unchecking the "Filter" box on the "Logs" tab - this will then start to display ALL events on your device which can be a lot.
So, click the "Connect" button, then try to click the "Clear" button right before you try to start your app, then as soon as your app crashes, disconnect your device from the IDE - this will help prevent too many extra events from being added to the logs list after the crash so it will be easier to see the events around the crash.
Post the log events related just to when you tried starting your app and that will hopefully give us an idea of what might be the problem.