Before you send it away ...
Sorry if you've been through this already
Sometimes it's just a matter of settings, plumbing and the pump rating
I see online it's suggested to run a pump of between 200 and 350 gph
If your pump is larger than that, it will take a very long time to cool down your tank as the water isn't being chilled much
If you haven't already been through this, I have these questions;
What flow do you estimate you have running through it
How long does it take to turn on once it hits the set temp
What hysterisis do you have set