FastAPI Python + ReactJS frontend assistance

I have a local Python app running FastAPI, with the endpoint if working properly. I also have a local ReactJS app running that i am trying to call FastAPI from. For some reason this isn't quite working. I need a maximum of hour of your time for your insight into how to get this communicating (perhaps i'm missing something obvious). I'd be looking to get on a quick call to share my screen to show you the application, and go from there.