The tag below your question indicates that you are using TurboTax Live. If that's true, you should address your questions to a TurboTax Live tax expert. You are paying extra for that service. See the following FAQ for instructions to contact a TurboTax Live tax expert.
How do I connect with a tax expert in TurboTax Live?
In TurboTax Online you cannot make changes directly on a form. Everything has to be done through the question-and-answer interview. What specific box on Form 8862 do you need to uncheck?
What is the exact message telling you that you can't file unless you leave the box unchecked - the entire message, word for word?