To get a successful response, make the requestTimeStamp match exactly the responseTimeStamp and you will get a successful 200 OK response. You can also use the time in the Response Header's "Date" but you should use the format month/day/year (e.g. 10/04/2019) and then you should use the exact time.
But my recommendation is for you to make the requestTimeStamp match exactly the responseTimeStamp, as that is easier for you to copy and paste. Refer to Request payload, Response payload, Response Header and screenshots below.
Try this sandbox test again and please share your results with us. I'm happy to help you with any further issues you may have.
"requestTimeStamp": "10/04/2019 5:49:59 PM",
"statusDescription": "Vendor is not configured for this transaction. Please verify",
"responseTimeStamp": "10/4/2019 5:50:13 PM",
Successful Response Header:
Status Code: 200 OK
Server : nginx
Content-Type : application/json;charset=utf-8
Content-Length : 176
X-SERVED-BY : l73c014
X-CORRELATION-ID : 1570211413_067_583295606_l73c014_VDP_WS
X-Backside-Transport : OK OK,OK OK
Cache-Control : no-cache, no-store ,no-cache, no-store, must-revalidate
Pragma : no-cache
Expires : -1
X-OPNET-Transaction-Trace : a2_ec79119c-de6b-4834-aadf-d090ccad0141-7964-43
X-AspNet-Version : 4.0.30319
X-Powered-By : ASP.NET
X-Content-Type-Options : nosniff
X-Frame-Options : SAMEORIGIN
X-XSS-Protection : 1; mode=block
Content-Security-Policy : default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline';
X-Global-Transaction-ID : 1295318927
X-APP-STATUS : 200
Strict-Transport-Security : max-age=2592000;includeSubdomains
Date : Fri, 04 Oct 2019 17:50:13 GMT
Connection : keep-alive
For troubleshooting steps on VCES iFrame, you can also refer to this community forum link - https://community.developer.visa.com/t5/General/Error-404-Visa-Card-Eligibility-iFrame-API/m-p/13021...
Can you please let us know what APIs are in your project?
Can you please let us know if you're issue is resolved? I'd be happy to help if you need further assistance.