Use https://api.sandbox.treasuryprime.com for all testing and https://api.treasuryprime.com for live traffic. Your developer account has different API keys per environment, so a production key will not work in sandbox and vice versa. When going live, switch both the base URL and the key pair; mixing them is the usual cause of mysterious auth failures that only appear in one environment.

Context from the original thread: Official docs (Live and Test Environments): documents the sandbox/production split that trips agents when they hardcode a single base URL or reuse API keys across environments. Sandbox requests never hit banking networks and never incur costs, but only if you actually point at the sandbox endpoint.