App Inventor Authentication and Function calls/returns

I am trying to figure out how to build out a seemingly simple app to communicate with my Particle Argon (I am learning new IoT things on my own).

I am able to authenticate and make the LED turn on and off using CURL using both inline and HTTP authorization. However, I am unable to get the App Inventor to connect successfully with a confirmation.

At the simplest proof-of-concept level, I want to be able to tap a button, the LED goes to that state, and I get the confirmation into a label. Literally a GUI version of what CURL does.

Once that works, then I want to add a functionality using GPS coords. But i'm at the baby steps phase right now, and confused because all my googlefu is taking me to threads with old information or information that looks right, but I don't so much as get an error returned or anything.

My objective/hope is that whatever the function returns is what will show up in the ReturnVal label, hence the name of the label. It comes back in CURL as a JSON response, so to me that should be doable?

Screenshot 2025-02-22 at 1.53.34 AM

I'm not very familiar with AppInventor, but it looks like you're trying to call a function on the device. It looks like in one step you have a join of param= and global SwitchVar. When calling a function with URL encoded post data, it should be arg= instead of param=