The Brain tree.

Missing, invalid, expired or revoked API key. Also returned when the person behind a "You" key is no longer a workspace member.

The key is valid but access is denied - the workspace is neither on a
paid plan nor a partner workspace (gated_plan), the workspace
override is off (gated_workspace_disabled), the whole API is
switched off (gated_kill_switch), or the requested workspace does
not match the key.

Over the per-key limit (300 requests/minute).