E-file reject code IND-507-01 usually means that someone else has already claimed your dependent on their return. This could be the other parent or even the dependent themselves.
Dependents cannot be claimed on multiple returns, and the IRS rejects any extra attempts to claim the same dependent.
For confidentiality reasons, the IRS cannot disclose who claimed the dependent.
See this TurboTax Help for how to resolve the e-file reject code.