P.M.
It's really common for poop training to come later, sometimes by several months. The sensations are different, more effort and time are generally required, it often includes some amount of discomfort, either from the movement itself or from sitting long enough to finish the deed (toilet-seat pressure and/or tingly legs).
And while the urge to pee is hard to hold back once it hits, the normal peristaltic action that helps push out a poop is very easy to disrupt with just about any sort of distraction, just as normal breathing is very easy to disrupt when there is emotional tension or excitement. And not even all adults can 'produce' at will – I seldom can.
So be patient. He might get the most success if his BMs are pretty regular and you can put him on the potty when he's most likely to have a bowel movement. Keep it relaxed, maybe read to him, and if he's 'tried' or sat patiently for several minutes, let him go play. He'll get there eventually.