Can't resolve Aurora serverless PgSQL10 DB from the VPC but Data API works

I'm trialing RDS Aurora Serverless - postgresql 10 flavour and have an odd issue, probably a config step I missed.
I've created the DB fine, xREDACTx-rds.cluster-xREDACTx.eu-west-1.rds.amazonaws.com comes up as available, in the vpc (only one in the A/C) .
The query editor allows me access to the db, can connect to the db and create / modify users, query and so on without issue.
However from a AWS Linux2 node within the vpc I can't resolve the endpoint as advertised on the connectivity & security page ( nslookup reports NXDOMAIN ).
I've followed the documentation and steps on connectivity issues / but this case isn't covered.

Is there something simple I'm missing here ?

VPC has DNS resolution enabled and DNS Hostnames selected - is there additional dns configuration required to expose the serverless endpoints to ec2 nodes within the vpc ?

Note: vpc is in 172.31.0.0/16 whereas a select from pg_stat_activity from the cli query editor shows the db client ip as 10.1.13.118 (port:29947 type: client backend)