If the back door opener does not operate, there may be a problem with the back door opener system. Have the vehicle inspected by your Toyota dealer immediately.
The following steps may be used as an emergency measure to ensure that the back door can be opened from the inside.

Remove the cover on the back door trim.

Tear the plastic film. Remove the cover.

Pull the lever.
If you lose your keys
If the electronic key does not operate properly (vehicles with a smart key
system)Airbag Signal Malfunction/Not Input (B15C4)
DESCRIPTION
If the DCM (Telematics Transceiver) detects an error in the communication between
the DCM (Telematics Transceiver) and center airbag sensor assembly as a result of
the DCM (Telematics Transceiver) self check, this DTC will be set.
...
Downhill Assist Control Indicator Light Remains ON
DESCRIPTION
When the downhill assist control switch is turned on, the downhill assist control
function is available and the downhill assist control indicator light illuminates.
WIRING DIAGRAM
Refer to Downhill Assist Control Indicator Light does not Come ...