Robo hi, I've checked your logs (you can do that at https://freeflarum.com/settings/logs) and found the following error:
[2021-12-09 10:34:36] flarum.ERROR: Exception: Received error [{"errors":[{"message":"You currently have
Essential access which includes access to Twitter API v2 endpoints only. If you need access to this endpo
int, you’ll need to apply for Elevated access via the Developer Portal. You can learn more here: https://
developer.twitter.com/en/docs/twitter-api/getting-started/about-twitter-api#v2-access-leve","code":453}]}
] with status code [403] when retrieving token credentials.
I don't use Twitter or their API, so I can't help you with this. You can visit the link shown in the error to learn more though...
songhuajiang it is indeed possible that it's because you are from China. When I visited one Chinese website today, it had broken CSS too. This might be just a temporary issue (perhaps The Firewall is too aggressive). Either way or not, I can't do much with this to help you.