Hi Steve, great you are enjoying yourself.
In Carrara ambient lighting is set at 20 percent by default - just to annoy us.
In the instances list see where it says Scene ? (instances list is that list at middle to bottom right that shows what is in your scene, click on the word “Scene, then up the top you will see some new windos at top right , One of them will habe the ambient setting in it - drag the thingy all the way to the left.
If you cant get shaddows on your robot still, make all the lights invisable, then drop a bulb really close to the robot on the right and see what happens - If no shadows, maybe he is floating off the floor, maybe he has his shadows turned off. Maybe you have shadows turned off in the render room though the light at the back indicates this is not the case?
Nice r enders by the way.
HINt to get your light to be close to the robot, select robot, hold down shift key and select light, then use ctrl k and this will bring up the align tool