Hi Guy
I have download the TheAPP.apk file to my PC, the run it on a android emulator, and it occurred an expected error. (Other local app package is not working too)
The Appium server from SauceLabs runs on their servers, inside their network. They can’t access your local file system.
You must either upload the app to their server ( Mobile App Storage | Sauce Labs Documentation ) or upload the app to a public location that can be accessed by their Appium server.
File names are not unique and SauceLabs will use the latest version. The id is more predictible (you can get the Id in the App Management page, click on the cog to the right of the uploaded app).