I'm trying a very simple Adaptive Form form POC, just to demonstrate the functionality in action end-to-end.
I've created a form, added it to a page, and can successfully submit it to where it displays the configured "Thank You message".
However, no call is made to the REST endpoint to submit the form data!
I see this error in the log:
08.11.2017 02:49:34.810 *WARN* [0:0:0:0:0:0:0:1  POST /content/forms/af/free-trial/jcr:content/guideContainer.af.internalsubmit.jsp HTTP/1.1] com.adobe.aemds.guide.utils.SubmitDataCollector templateKey not found in merge json:submissionMetaInfo
That's a warning & submission should still work. I assume you are using post method for submission. You can probably enable HTTP Components log and see what is happening. May be wireshark or Charles with reverse proxy could help if call is orginating but failing on receiving end.