Thanks @Olamihybr,
Just confirming you have your Sandbox access and secret key with the Sandbox request URL.
https://sandboxapi.rapyd.net/v1/data/countries
Are you making your request in Node.js?
If you havenβt made any test request yet, hereβs a simple guide of making a request in Postman with your Sandbox credentials.
Hereβs a comment with more resources, however these may be address a different error related to when the The API received a request, but the signature did not match.