We acknowledge the impact this might have caused. Hedera has resolved the issue, and services have resumed.
During the outage, Hedera discovered a race-condition was the cause of the error. A new patch was deployed via a release candidate and has since fixed the error. For further information, please see the release notes.
https://github.com/hashgraph/hedera-services/releases/tag/v0.7.0-rc2

A fix has been implemented and we are monitoring the results.

The issue has been identified. The Hedera team is working on a state restoration and plans to bring services back online by 8/26/2020. In the meantime, the Preview - Testnet is available for usage.

Hedera is observing a network-wide outage on testnet. We are investigating the cause and working to mitigate the impact on applications. The Hedera previewnet is still online.