All clients that relied on the testnet Hiro API. This includes the Explorer, Hiro desktop and web wallets, the stacks CLI, and others. Requests on all endpoints to the testnet API were unable to be served.
Cloudflare, our network proxy provider, experienced an outage affecting most downstream client services.
https://blog.cloudflare.com/cloudflare-outage-on-june-21-2022/