Dynamic Grabber issue - Cafe World

I followed the tutorial for making dynamic grabber code pieces and I'm having an issue here.

I created a grabber command below and it doesn't seem to be getting triggered. The entry for the feast invite is still shown in FBWM with a white bg as if it has just been skipped.

{"appID":"101539264719","link":"Claim Feast Invite","ret":"dynamic","note":"CUSTOM Grab"}