Then the issue is with FreeNom. As your Nameservers are not fully propagated. I would try waiting a few days, and if the error still occurs, check back in.
EDIT: You could also try using a different network/device
I also have same issue. my domain (at freenom) had been set to point to ns1.epizy.com and ns2.epizy.com. a week ago it stopped working. maybe the issue is with episy name servers?