This error can occur for several reasons, such as server-side issues, network problems, or issues with your Riot Games account. Here are some steps to try and resolve the issue:
Retry Later: Sometimes, server issues are temporary. Wait a bit and try again later.
Check Your Internet Connection: Ensure your device is connected to a stable internet connection.
Clear Browser Cache: Clear your browser's cache and cookies, then try signing up for the beta again.
Use a Different Browser or Device: Try using another browser or device to sign up.
Contact Support: If the issue persists, contact Riot Games Support for further assistance.