Sometimes it is due to the network connection, sometimes it can be temporary problem on the testnet. you can try with a different net connection, and also wait a few minutes and try again.

In addition, if you know programming, you can easily get testnet tokens using this guide: https://sdk.mystenlabs.com/typescript/hello-sui

You can try using an alternate method. Check out this link for details: https://docs.sui.io/guides/developer/getting-started/get-coins