Dnspod change nameserver error

dnspod change the nameserver shows it is not valid. nameserver1 is ok, but namesever2:vicky.ns.cloudflare.com not valid.what should i do?

I dont know what dnspod is, but vicky is a valid nameserver.

Post a screenshot of the error.

my domain suffix is: .top, it maybe not support three level domain name

No that wont be the issue.

but is can’t change to vicky.ns.cloudflare.com

I dont know what the screen says. Can you post an English screenshot?