Puppy training commands

This post may be a bit trivial compared to some other people questions and struggles so apologies

I have an English Springer Spaniel from working line, so as you can imagine, he is very intelligent and loves to please.

For this reason he has been so easy to train and at 3.5 months he can sit, stay, come, leave, drop, place, off, toilet and even spin.

When training he just is not grasping down, he will only go down if a take my entire hand to the ground with the treat however, in a normal setting when I say down he will lie down!

Any ideas on how to get him to do this during training?

For context, I have only attempted and success with down on command on the sofa when we are both on it and he is unsettled, but I want to be able to teach him to go to his place and then down for whilst I am busy in the kitchen which I need him to consistently follow through my command for this to be possible.

I’m aware he is only 3.5 months and he is doing amazing for his age, I just can’t understand how he can understand the more difficult commands easier than a simple down! 😂