Unable to adjust volume of an external effect in Control Room

In this video https://youtu.be/4wPbyoLDcfw, I first show how adjusting the volume works for a Bitcrusher inserted. After that, if I turn on an external effect, I lose the ability to adjust the volume from the Control Room. Am I doing anything wrong?

Turns out the routing on my interface wasn’t set up properly, I fixed it with this setting. I connect to the effect via SPDIF.