[VetteVet]

It's quite simple really. The parking lights operate off the headlight switch and the turn signals work off the turn signal switch. They are on entirely different circuits. The parking lights work off the brown wire and if you aren't getting power to the brown wire then they aren't going to work.
As I detailed above, the front and rear parking lights are powered by different brown wires so the rear lights may work and the fronts may not.

It's also true that the front and rear turn signals work off the same circuit so all four including the marker lights are powered by the same wire. It's a purple wire in the center of the steering column connector.

If you have no power on the brown wire then it stands to reason that they are not going to work.