Hub Link - not sending commands to SmartThings hub?

I set up my first webCoRE piston using a linked motion sensor and dimmer switch from my existing SmartThings setup. The devices all appear in Hubitat, and the status of those devices gets updated when something happens on SmartThings.

However, when I try to control a device from Hubitat to SmartThings, the command seems to get lost along the way. In the Hubitat logs and device status, I see that the command ran, and the device state is updated in Hubitat (so as far as it knows, it happened), but there is no activity on the SmartThings side.

I set up Hub Link, and Send Hub Events, with the corresponding IPs for ST and Hubitat respectively.

Any ideas? I can provide screenshots or logs, if there is anything that can help.

Hub Link only works one way, from ST to Hubitat.

Well I feel foolish now! I remember reading that, but just forgot, had gotten to thinking that each side was pushing to the other, not a sender->receiver relationship. Also compounded because my only other automation that I set up was using all hue lights, which are just connected to both systems since they run though the hue hub.

I guess I will work on moving some more of my devices over!