Help with Web API POST requests and Body

What would be the web api BODY looks like (& how to compose it) if I want to send a POST to Google Apps Script (GAS)?
I have the URL from GAS and it works when I test it.
I have researched to pass parameters and Headers in POST, but so far I am unable to compose the body of my POST request correctly. I tried many combinations and all I get is Undefined for my data.
Any help would be appreciated.

If you give me a link to your project with access to GAS, then I’ll work on finding a solution.

I have a similar problem… for one thing, we can’t set headers in block code so that’s that :frowning:
But the worst is: my request body doesn’t get sent at all…!?!
I changed my Heroku app to respond with the whole body of the request and what I get is empty; so the body is never reaching my app…

(my Heroku app works perfectly with anything else, I’m looking to turn it into a phone app with Thunkable but it’s proving a lot more difficult than this should be…)
What am I possibly doing wrong here?

(I also tried to hardcode a body in the webapi object in design mode but that doesn’t get sent either)


edit: since I couldn’t change the headers via blocks, I wasn’t even trying, but now I tested hardcoding some headers and they don’t seem to be sent either…