No usable credential on the request

No API key, or one that does not authenticate. The answer is deliberately uniform: an expired key, a revoked key, a key for another environment and a key that never existed all look the same from outside, because telling them apart is a way to find out which keys exist.

What to do

• Send Authorization: Bearer pg_test_… (or pg_live_…). Not Basic, not a bare key, not a query parameter.
• Check the key is for the right environment. A test key against the live host is this error.
• Check the key has not been revoked or rotated out in the dashboard.
• If you are running through a proxy, check it is not stripping Authorization.