18 month old crying at the gym daycare?

I took my 18 month old to the gym daycare and he was fine at first. He ran in and started playing. They called me about 30 min later and when I went in I found him crying so hysterically he could barely breathe. When he saw me he reached for me and when I held him he stopped crying right away. This same scenario happened when he was 13 months old. I figured 5 months later he would be able to adjust but no, same thing. Why is he crying like this, not when i drop him off but 30 min later?