Going on the assumption that the problem is the ***trunk*** won't close by pushing the ***button***. VehicleHistory.com has a page devoted to the subject on your SUV here.
[link|https://www.vehiclehistory.com/articles/toyota-highlander-power-rear-door-not-working|Toyota Highlander: Power Rear Door Not Working? - VehicleHistory|new_window=true]
Here are a couple of highlights from that page.
[quote|format=featured]* The quick fix for this problem may be to press and hold the rear liftgate close button. It will beep several times and then let go. This will reset the liftgate and allow it to work properly in most cases.
* check the on/off button inside the glove box.
* Locate the close button on the rear liftgate door. It is only accessible in the liftgate door jamb when the liftgate is in the open position.
* Press and hold that button for a few seconds. You should hear it beep about four times.
* Release your finger.
* Then, press the button again quickly to signal to close the door. This should fix the problem and allow it to close normally.[/quote]
Those are a few things to check. Try out these fixes and let us know what happens.