It's the fact that your $6000 of income was not reported on a form W-2, making it more than a "simple" return.
For more discussion and options, see https://ttlc.intuit.com/community/taxes/discussion/this-said-it-was-free-and-now-it-s-making-me-upgr...
How was you income reported to you? If it's stipend income, under $13,850, it may not need to be reported.
