I have seen the support guide before but the domain used to work before, if the domain was owned by someone else it should not have worked in the first place. Moreover I also tried to use external dns service and it is still not working.
You can continue posting here about the issue, but there’s absolutely nothing we can do about it. You can make your call if you wish to get it cleared with NS1 or not.
Since you’ve already added the domain to the site, I don’t see why using external DNS would not work. Could you clarify what do you mean it’s not working? As far as I can see, you’ve not configured external DNS at all:
dig A +short avirana.com
>
dig CNAME +short www.avirana.com
>