Turn signal indicator 64 Barracuda- help me understand

THAT INDICATOR LAMP DOES NOT GROUND and is not supposed to in this application, here is how it works

The lamp is connected between the hot leads to the left and right indicator lamps. Those lamps are grounded, and they are large wattage, that is, low resistance lamps. The indicator is a low wattage, that is, higher resistance lamp

When you "let's say" signal to the left, the left side is flashing and the power from the left front feeds to and through the indicator lamp. HOW does it get a return path? Easy. It goes to ground through the RIGHT side lamp.

This puts the two lamps in SERIES. Because of the wattage difference, the indicator lights up bright, and the unused front lamp likely does not even glow. The lamp doing the turn flash up front of course is unaffected, and flashes normally

How to get it working? Obviously somting wong

Are both front lamps working properly? That of course is the first thing because if one of them is not grounded, or not getting a power path through the bulb, then the indicator won't work on either side

By the way an LED will not work in this case, it must be a "plain ol lamp."