What are you trying to connect to?
I try to test connection from the tableau server to redshift and postgreSQL postgreSQL is in the same tableau server machine, redshift is in another cluster.
if I ssh the tableau server, I can access the redshift (using a python script) and the postgreSQL (command: psql -h ip-10-123-30-20 ....), ip-10-123-30-20 is the hostname of the tableau server. which means network connection is ok. no firewall block.
But if I access the tableau server from webpage (the one with port 80), goto Explore All Data Sources (on left of the page) , filter (on the right of the page) to Connection Type -> choose Redshift -> choose any workbook -> choose … (3 dots) -> edit connection->test connection fails. Same thing if I choose Connection Type as PostgreSQL it fails too
Besides, if I access the tableau server webpage (the one with port 80), goto status -> goto Traffic to Data Source -> it showed error like Unable to connect to the PostgreSQL server "ip-X-X-X-X".
in summary, the network connection between the tableau server and its data source redshift and postgreSQL is ok but tableau server cannot set up connection to them from web page.