This means your endpoint has authentication turned on (from the Keys & Secrets tab of your API project), and the request either didn't include a valid key, or didn't include it in the way the endpoint expects.
What to check
- Is the key still valid? If it was regenerated or revoked since you last copied it, the old value stops working immediately, generate a fresh one if you're unsure.
- Is it actually being sent? A key that's correctly generated but never attached to the request (stored in a variable that's never used, for example) produces exactly this error, double-check it's genuinely present in the request, usually as an
Authorizationheader. - Is it the right endpoint? Confirm you're calling the endpoint you think you are, a similarly named but different endpoint might have different authentication requirements.