GatewayToken Not working

Sandbox Signup
#1

While generating gateway token we are able to receive token but that token is not working for other api’s. Please check the credentials and error below
Credentials
{

"clientId": "SBX_003722",

"clientSecret": "d922****-****-****-****-*****8584103",

"grantType": "client_credentials"

}
Error:

<title>Request Rejected</title>
The requested URL was rejected. Please consult with your 
administrator.<br><br>Your support ID is: 8374555060843741135<br><br><a href='javascript:history.back();'>[Go

    Back]</a></body>