Dependent

In Turbotax I answered questions for dependent and based on my answers grandchild is set as dependent.  Grandchild lived with me for complete year, is in high school, no other relative lived with me and I provided all support.  When I electronically submitted Fed tax return it was rejected be cause grandchild SSN was on mothers Fed Tax filing.  Answering the step by step questions there is no option to show grandchild was claimed as a dependent on another persons tax return.  How do I answer the question accurately and not have the grandchild show up as dependent to keep return from being rejected.  Is there a way to get tax deduction and not claim as dependent?