Resolving a connection string to a target Oracle database

[Demetrius]

We are using Qlik's Data integration tool to replicate data from one on-prem Oracle database to another.

We have been able to establish a connection to the source server.  But cannot do that to the target server.

We are using the connection string 

(DESCRIPTION= (ADDRESS=(PROTOCOL=TCP)(HOST=<server name>)(PORT=1521)) (CONNECT_DATA= (SID=<sid name> ) ) )

For both the source and target.  Our Admin could not find where it is using TNS Names anywhere on the gateway we have set up.

Does anyone know where this happens or have an idea about what the source of the problem is?

Thank you.