Establish a Confidential Client

    @PostMapping(path = "/verify", produces = {
                    MediaType.APPLICATION_JSON_VALUE })
    public ResponseEntity<Registration> verify(@RequestParam(name = "token") String activationToken,
                    @RequestBody(required = false) Registration registration, final HttpServletRequest request,
                    final HttpSession session) {

            final RequestContext requestContext = OktaUtils.constructRequestContext();

            AuthenticationResponse beginResponse = idxAuthenticationWrapper.beginUserActivation(activationToken,

  "Begin Response Status {}",

             return new ResponseEntity<>(HttpStatus.OK);


Okta returns error: Error Detail: [invalid_request:Only confidential clients can use the activation token flow]

Question: How do you establish a confidential client?

I have configured in the Admin Console with multiple different Application types with Client Secret and Interaction Code enabled but unable to determine how to establish a confidential client for the SDK (GitHub - okta/okta-idx-java: okta-idx-java).