Unable to connect to a PostgreSQL Database

I’ve been trying to establish a connection between JabRef 4.1 on a Mac OS X 10.13.2 x86_64 (Java 1.8.0_152) system and a PostgreSQL (9.4.15) database located on a Raspberry Pi 3 in my local network. I’m able to manage the DB-Server using pgAdmin4 and connect via python’s psycopg2 package from the Mac which tells me that the DB-Server is reachable. Similarly, a docker container running on the Pi itself is able to use a different database on the same instance without problems. Nonetheless, each time I try to connect to the empty ‘jabref’ database using JabRef’s ‘Connect to shared database’ feature I get a “Connection Error: Password authentication failed for user” message.

The DB-User I’m trying to connect with is the owner of the ‘jabref’ database and has privileges to login, create roles and create databases. It is also the same user I’ve used to connect via pgAdmin and python on the Mac. Has anyone encountered a similar issues using PosgreSQL? A few days ago I tried the same procedure on a Windows 7 machine running both JabRef 4.1 and PostgreSQL 10.1 locally (i.e. via localhost) without success. Once I switched to an empty MySQL database on the same machine everything worked as expected.