After yesterdays maintenance window I started to see Invalid API Key
errors returned from the Etherscan Sepolia API endpoint. This API key I'm using was working before yesterdays maintenance, and any new keys created run into the same issue.
https://api-sepolia.etherscan.io/api
?module=account
&action=balance
&address=0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae
&tag=latest
&apikey=$API_KEY
{"status":"0","message":"NOTOK","result":"Invalid API Key"}
Goerli and Mainnet still work fine.
Best Answer
Seems to be fixed after Scheduled Maintenance for Web (Testnet)