I replaced one of the rear taillights on my previous 4Runner after I backed into the damn garbage can and it shattered the passenger side taillight. :bonk:
That's exactly what I did!!! Couldn't believe it broke, I barely tapped it.
And then that the dealer wanted $240 for it! Got it online for $160 shipped and was surprised that it was the complete unit.
Anyway, after I replaced the rear taillight I had various problems getting it to work such as the taillight didn't work, the turn signal didn't work, etc... All the issues I experienced were related to me not connecting the various connectors for the multiple lights in the taillight assembly correctly. It's a little tight in there.
As other folks have mentioned, make sure the bulbs are in correctly and reseat the connectors.