In case your remote just won't work and you have already tried replacing the batteries, this guide will walk you through removing the front cover and replacing the remote sensor on the inside of the cover.
Unscrew the five 0.31 inch T-9 screws on the back cover.
Slide the cover towards the back until it is no longer under the front cover.
Lift the cover up and off the device.
Unplug the ribbon cable from the motherboard. Some force may be required for this step, so be careful not to rip the ribbon cable.
Unscrew the two 0.31 inch T-9 screws on the inside of the front cover.
Use a spudger to push the three tabs on the inside of the front cover up and forward to release the cover.
Unscrew the two 0.31 inch T-9 screws on the back of the sensor.
Lift the sensor up to remove it.