Help Setting Domain Keys and DKIM

Help Setting Domain Keys and DKIM

I've following tutorial to set domain key for my zoho mail account, but I'm stuck in step 7 ("Click Start Authentication").
 
I'm using DNS Hosting from NameCheap.com, and after I check it with MX Toolbox it shows that the TXT record already exist in DNS. Even so, I still fail to start authentication process.

Did I do something wrong ? Please help.