That response should indicate that the file was saved successfully, so make sure you're looking in the right location when verifying that manually, e.g., on the Dropbox web site.
For instance, check that you're signed in to the same account that you're connected to on the API (or at least, an account with the relevant shared folder if you're uploading to a shared folder).
Also, if the account is on a team with the "team space" configuration, note that by default these API calls operate in the "member folder" of the connected account, not the team space, so make sure you're looking inside the member folder (i.e., the folder with the member's name) and not the team space itself. (You can configure API calls to operate in the team space instead though. To do so, you'll need to set the "Dropbox-API-Path-Root" header. You can find information on this in the Team Files Guide.)