1988 Volvo 240 DL with about 300k miles

The two bottom red tail lights don't work when I turn on the headlights. However, everything else works on both rear lenses, i.e. the back-up lights, turn signals, flashers, and brake lights (the left rear red lights come on when I turn on the headlights.

The right rear lens looks newer. I switched out the left side's bulbs, but the right side bottom red lights don't work.

Thanks in advance