Etherscan's V1 API was retired after August 15, 2025. Current integrations should use the V2 API, explicitly select the intended chainid, and use an Etherscan API key. An old explorer-specific key is not automatically a substitute. See the retirement notice and V2 documentation.
In the Etherscan discussion, include the network when describing a result. Compare a known transaction on that same network before moving a production workload; a syntactically valid address does not establish which chain's history you requested.
Akousa