Welcome to Vue Designer 
@tstuempfig
Are you able to kindly share some screenshots or screencast to help troubleshoot this issue? What’s backend, and what errors are you receiving at your backend?
Does your app work outside Vue Designer when starting your dev-server and testing it out in your external browser?
Meanwhile, can I recommend you to check these two threads that cover how to navigate to a page behind authentication - Laravel + Inertia + Vue - #2 by TechAkayy
Also, you can also use Vue Devtools, access it from the State Panel, please refer to this thread for more details - It is possible edit secret page - #4 by TechAkayy
All the best!