My guess is that the GeoCoder transformer wants some kind of authentication. Because you’re not passing any, it’s failing. I tested the geocoding service and it looks like it does not require any authentication. You can get the same results using an HTTPCaller transformer and just call the REST endpoint directly.
You can enter the address here, or better yet, use a parameter or attribute value
f
json
outfields
*
Note, you can limit outfields to whatever you want. But * will give you everything that the service outputs. From there, you'll get a JSON in your _response_body attribute which you can parse using the JSON transformers.