I am sure you are getting a response but unless it is in the exact form ember expects then it will not automatically extract the ID and update the store. Take a look into the normalizeResponse, specifically normalizeSaveResponse which is the hook you can use after saving a record.
were you ever able to find an answer to this? I am having the same issue, but no luck. I’ve seen alot of questions like this from several years back, which included workarounds, but none of the workarounds really worked for me. Basically, i only get back the data that i included in the “CreateRecord” part, but not the id that came from the server.