Missing nameservers reported by parent and your nameservers

The nameservers currently listed at the .pt top level registry are ns1.esoterica.com and ns2.esoterica.com. When I query those two servers, neither of them has any information about your domain, so they can't answer DNS queries. Obviously I can't know whether esoterica.com are your old or your new provider, but it's obvious that the .pt registry is not in sync with your actual nameservers.

When you are changing your nameservers, you need to be aware that changes of glue records at the top level registry aren't instantaneous. The zone file for a TLD is usually very large, and reloading it takes time - they can't do it every time someone wants to make a change, instead it's scheduled to reload at intervals. The length of those intervals can vary. So, when you are changing nameservers, it's best to do it in several steps:

1. Make sure your new nameservers are handling your zone correctly before you do anything else. You can test this even before the TLD glue records are changed, by running your domain through DNSCheck for undelegated domains.
2. Change the glue records at your TLD.
3. Wait - at least a couple of hours, possibly a day.
4. Check that dig caixasbaratas.pt now returns the new glue records
5. Wait another day, to allow any cached information around the world to expire
6. Remove your zone from the old nameservers

By going this slowly, you can be certain that your domain does not become unreachable due to glue record mismatches.

I had same problem and it was gone after adding these lines to my zone file:

@       IN  NS      ns1.example.com.
@       IN  NS      ns2.example.com.

Some notes:

• Don't forget to increase SOA serial number after changing the zone file. (for example adding those two records)
• if you're using @ in your records don't forget to define its value using $ORIGIN example.com. at begin of your zone file.