I checked your domain and it seems to be working fine from here.
If the domain is less than 72 hours old, then this is probably just DNS caching, and the issue will resolve itself automatically soon. This article has more details:
If it has been more than 72 hours, then it might be a security filter on your end that’s blocking access to the rf.gd. Here are some things you could try to verify:
Try using a different DNS resolver, like Cloudflare’s 1.1.1.1 on your device to rule out a blocking issue.
Check your website from a different device or network.
Verify that the URL https://cpanel.rf.gd loads for you, to check if it affects the entire rf.gd or specific websites.