Receiving error: JWT signature invalid, when using the sample code shared.

{myloginur}?kind=error&message=JWT+signature+invalid.+The+signature+cannot+be+verified%2C+check+that+your+tokens+match

I enable the JWT seeing the details here
https://support.zendesk.com/hc/en-us/articles/203663816-Enabling-JWT-JSON-Web-Token-single-sign-on

My configuration via Admin Center.

1. Both SAML(using for some reason) and JWT is enable.
2. In EndUser section, I tried enabling the ExternalAuthentication tried with both enable and disable.

Receiving the same error.

Code snippet

Date now = new Date();
Date expiryDate = new Date(now.getTime() + 6048000);

String jwtString =  Jwts.builder()
        .setIssuer("zendesk")
        .setSubject("zendesk-user")
        .setId(UUID.randomUUID().toString())
        .claim("email", getUser().getEmail())
        .claim("name ", getUser().getName())
        .setIssuedAt(new Date())
        .setExpiration(expiryDate)
        .signWith(SignatureAlgorithm.HS256, SHARED_KEY)
        .compact();

String redirectUrl = "https://" + SUBDOMAIN + ".zendesk.com/access/jwt?jwt=" + jwtString;

if (returnTo != null) {
    redirectUrl += "&return_to=" + encode(returnTo);
}

return redirectUrl;