Send a test event
POST /endpoints/{endpointId}/test-deliveries sends a signed webhook.test event to the endpoint straight away, through the same signing, sending and logging as real events. The response tells you what happened:
2xx, succeeded is false, statusCode shows what it answered, and the test is retried on the normal schedule, so you can watch a retry arrive. You can send up to 5 test events a minute per endpoint.
Receive deliveries on your own machine
Endpoints must be public HTTPS URLs, solocalhost is refused. While you build your receiver, use a tunnelling tool to give your local server a public HTTPS address, and register that address as the endpoint.
To look at deliveries before writing any code, point a sandbox endpoint at a hosted request inspector. Anything it receives is visible to whoever holds that URL, so use it only with made-up data, never point a live endpoint at one, and delete the endpoint when you are done.
Use sandbox
Build and test against sandbox (https://api.sandbox.flowpayroll.ai). Sandbox events carry "livemode": false; live events carry true. Each environment has its own endpoints and secrets.
See what your receiver answered
GET /deliveries/{deliveryId} shows every attempt: when it was sent, how long your server took, the status it answered and the start of its response body. It is the quickest way to see why a delivery failed.