I'd been an IT contractor for a very large corporation for about a year, and everything was going well; successful project involvement, great performance feedback, good relationships with internal customers. A few weeks before my one year contract expired, I started regular medical treatments (life-saving, totally mandatory) that take a few hours out of a few work-days per week. My immediate manager was totally OK with this, as I had briefed him ahead of time about what to expect. However, when my contract came up for renewal (which is considered routine), his manager, our group executive, told him not to renew it. I'm now out of a job.
Unfortunately, as an independent contract, you have very little recourse.
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Personal Injury Lawyer
Generally, there is no obligation to renew an employment contract. However, if the reason you gave and your suggestion that the refusal to renew was health-based your rights *may* have violate your rights. You should be able to get a free initial consult with one or two employment lawyers for free in your area of the state.