Getting 400 error in postman tool: "`api_key` should be minimum 6 characters in length."

Hi, I am trying to post "https://api.kite.trade/session/token" with below details in postman. But I am getting below response. Kindly help.
{
"status": "error",
"message": "`api_key` should be minimum 6 characters in length.",
"data": null,
"error_type": "InputException"
}

X-Kite-Version = 3
Also I have checked all the keys and they are as expected. For security purpose, I have made them as xxx,yyy & zzz in the screenshot.

I have used below java function for "SHA-256"
public static byte[] getSHA(String input) throws NoSuchAlgorithmException {
MessageDigest md = MessageDigest.getInstance("SHA-256");
return md.digest(input.getBytes(StandardCharsets.UTF_8));
}

public static String toHexString(byte[] hash) {
// Convert byte array into signum representation
BigInteger number = new BigInteger(1, hash);
// Convert message digest into hex value
StringBuilder hexString = new StringBuilder(number.toString(16));
// Pad with leading zeros
while (hexString.length() < 32) {
hexString.insert(0, '0');
}

return hexString.toString();
}

Called it as 'toHexString(getSHA(API_KEY + REQUEST_TOKEN + API_SECRETE);'

Please find the input parameters in screenshot below