Ethereum Mainnet Chain is synced again and our APIs are now operational. We apologize for the downtime and thank you for your patience.
As a summary of what happened:
The go-ethereum client on Ethereum caused an unplanned hard fork between older and newer releases (more details here)
As a policy we do not update systemically to the latest version unless strictly required as it's generally risky. We only update when the go-ethereum maintainers flag it as required. In this case the risk of forking was completely unannounced so we noticed just with everyone, when it happened.
Luckily we already had an upgraded version almost ready. We patched and re-tested the update as quickly as we possibly could and we're now starting to sync back from the correct fork.