Make sure that you are using same profile through which you
made a login previously. That works for sure.
The only thing that comes to my mind is that you accidentally
are creating new profile every time. So once you log in to
account, just edit or create new script so already created
profile is loaded again.
@marlo If you check append, previous file result won't be replaced, you probably have action, which doesn't have append checked. If you are 100% sure, that append is checked everywhere upload your project.