Every block explorer built by Etherscan ( eg. BscScan, PolygonScan, HecoInfo ) requires a different account to be created and hence a different set of API keys 🗝.
The additional endpoints available under any API PRO subscription are only available to the Binance Smart Chain mainnet, and not supported on the testnet.
A technical glitch may have occurred in the key creation process. In this case, try deleting the key and generating a new one ✨
If the issue still persists after using a freshly generated key, do reach out for us to have a closer look.