Hi, @davidrft, and welcome to our Netlify community site.
What domain name is this for? I see a Netlify DNS zone recently configured which I believe is the one being discussed here.
That domain is correctly using Netlify DNS when I test it now. My best guess is that delays in Netlify DNS taking effect had to do with the time to live values for the previous NS records for the domain.
The following community topic also discusses ways to greatly reduce time required for DNS migrations to take effect:
If the Netlify DNS configuration still isn’t working, please let us know.