Error establishing a database connection

I have a test site setup on Namesco hosted environment. https://www.readingroadrunners.org/web2
This is on test2 subdomain at the moment as using the root for our main site.
To test duplicating this accross I created a https://www.readingroadrunners.org/web3 subdomain folder I also set up a new database with identiacal credentials.
All runs fine with no errors. I click on Update permalinks and receive ‘Error establishing a database connection’ I’ve compared both wp-admin files and new one is in order. Any connections to web3 give the same error

I have a local Wamp instalation at home so also tried duplicating to this in a sub folder \localhost\roadrunners Again I created a fresh database with identical credentials with full admin access. I receive exactly the same database connection error.

Any help would be appriciated.
Thanks