JNLP Java Web Launcher

Desperate to use Java Web Launcher for ProRealTime charts (JNLP file), as it is required to migrate fully to Manjaro. Managed to get to work on Ubuntu, but not really an option. Unfortunately absolute newbie and time limited, although I have utmost determination, hence have tried various things inc installing java versions and with icedtea, but without success. Any help most appreciated!