I think the issue is that, you are not able to resume the workflow graph , after the interrupt is triggered. You need to use Command(resume="some value") to resume the workflow graph, after interrupt is raised.

Here is detailed approach on how to handle interrupts with FastAPI --- https://medium.com/generative-ai/when-llms-need-humans-managing-langgraph-interrupts-through-fastapi-97d0912fb6af