Zapier action showing "Stopped talking to" when used as @GPT

So, now that you can call GPTs from any conversation, I figured I’d make a GPT that creates a summary of the conversation and appends it to a Google Doc.

I have a working GPT using Zapier actions that successfully appends things to a Google Doc, when I start the conversation as a GPT.

But if I start a regular conversation, and @ Journal Assistant it, then I get “Stopped talking to”

Any ideas what might be going on here and how to fix it? Are there any known issues with custom actions and this @ feature?