DBLink problem between Oracle and PostGreSQL

Dear all,

I'm not sure if it is the correct address to send this king of request,
but we are currently struggling with a problem between Oracle and
PostGreSQL, passing through ODBC, so I take my change.
The situation is the following:
. On Oracle side:
 - Windows Server 2012 R2
 - Oracle 11g r2 (11.2.0.1.0)

. On PostGreSQL:
 - PostgreSQL 9.4.13
 - No details on servers or configuration, we don't have access to this.

. ODBC PostGreSQL Drivers 10.01.00.00

=> The problem is the following:
. We are currently unable to use a DBLink from Oracle to PostGreSQL, via
ODBC. The error received is: "could not connect to server: Connection
refused ".
. But in Excel, I can retrieve data from PostGreSQL using the ODBC
connection I'm using in Oracle.
. We have several other connections and DBLinks from the same Oracle DB
pointing to PostgreSQL 9.1.24, they are working fine - no problem.
(for info, we are working on Oracle for about 15 years now, so our
assumption is that our configurations are correct, as far as we can see)

=> My question is:
. Do you know if there is any kind of compatibility problem between
Oracle 11.2.0.1.0 and PostgreSQL 9.4.13? Have heard or read any kind of
problem like this?

Any help, any idea is welcome ..

Thanks !
Kind regards
Vincent