My 17-old (1.5) toddler is not consistently responding when we call his name.

We used to call our baby different nick names for almost a year and we started to stick to his First Name around 2 months ago. He sometimes ignore us or wont even look when calling his name. Unless we sing or ask him a to look at something for example. Paul - nothing Paul look here - nothing Paul come here - nothing Paul look at santa - he points and looks at santa Paul where is the christmas tree - he will point and look at the tree Paul + shaking food or toy - will look most of the time When the doorbell rings - will look at the phone When washing machine is on - will look and ask what's that When airplane flies - will point it and say airplane with byebye or hi hand gesture One thing they he does that will always look me in the eye is when he is looking at books with images and points to a picture. He will ask what's this, and look into my eye and pause for me to answer. Once I say the name of the image, he will look back at the image But he wont repeat what I said as if he understood and move on to another image. History: We had unlimited screen time since birth but we cut it to 0, around 2 months ago also.