Daphnis Nerii not moving
Wikipedia tells us the following about the larva of the oleander hawk-moth (Daphnis Nerii):


  Just before it pupates, the oleander hawk-moth larva becomes browner in color. The pupa of this species measures around 5.5 to 7.5 centimeters in length, and is light brown with black spots and a black line down the middle


The stage your critter is in probably resembles Fig. 1. It's probably fine.


Fig. 1. Caterpillar just before pupating. source: wikipedia