This relates to #3139 and #3153.

I am using LO 5.4.1.2 with Jabref on Debian 9. Connecting Jabref 3.8.2 is working without problems. When I try to connect Jabref 4.0, I have the previously reported connectivity problems.

[File:] grouptree.fxml not found, attempting with camel case Oct 05, 2017 12:33:54 PM javafx.fxml.FXMLLoader$ValueElement processValue WARNING: Loading FXML document with JavaFX API of version 8.0.112 by JavaFX runtime of version 8.0.111 File: grouptree.css not found, attempting with camel case 12:34:42.507 [AWT-EventQueue-1] ERROR org.jabref.logic.util.io.FileUtil - Error trying to locate the file unoil.jar inside the directory /opt/openoffice4 12:34:42.514 [AWT-EventQueue-1] ERROR org.jabref.logic.util.io.FileUtil - Error trying to locate the file jurt.jar inside the directory /opt/openoffice4 12:34:42.515 [AWT-EventQueue-1] ERROR org.jabref.logic.util.io.FileUtil - Error trying to locate the file juh.jar inside the directory /opt/openoffice4 12:34:42.515 [AWT-EventQueue-1] ERROR org.jabref.logic.util.io.FileUtil - Error trying to locate the file ridl.jar inside the directory /opt/openoffice4 12:34:42.516 [AWT-EventQueue-1] WARN org.jabref.gui.openoffice.OpenOfficePanel - Could not connect to running OpenOffice/LibreOffice java.io.IOException: (Not all) required Open Office Jars were found inside installation path. at org.jabref.gui.openoffice.OpenOfficePanel.loadOpenOfficeJars(OpenOfficePanel.java:438) ~[JabRef_4.0.jar:?] at org.jabref.gui.openoffice.OpenOfficePanel.connect(OpenOfficePanel.java:388) ~[JabRef_4.0.jar:?] at org.jabref.gui.openoffice.OpenOfficePanel.lambda$initPanel$1(OpenOfficePanel.java:146) ~[JabRef_4.0.jar:?] at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) [?:1.8.0_141] at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) [?:1.8.0_141] at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) [?:1.8.0_141] at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) [?:1.8.0_141] at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) [?:1.8.0_141] at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289) [?:1.8.0_141] at java.awt.Component.processMouseEvent(Component.java:6533) [?:1.8.0_141] at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) [?:1.8.0_141] at java.awt.Component.processEvent(Component.java:6298) [?:1.8.0_141] at java.awt.Container.processEvent(Container.java:2236) [?:1.8.0_141] at java.awt.Component.dispatchEventImpl(Component.java:4889) [?:1.8.0_141] at java.awt.Container.dispatchEventImpl(Container.java:2294) [?:1.8.0_141] at java.awt.Component.dispatchEvent(Component.java:4711) [?:1.8.0_141] at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888) [?:1.8.0_141] at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525) [?:1.8.0_141] at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466) [?:1.8.0_141] at java.awt.Container.dispatchEventImpl(Container.java:2280) [?:1.8.0_141] at java.awt.Window.dispatchEventImpl(Window.java:2746) [?:1.8.0_141] at java.awt.Component.dispatchEvent(Component.java:4711) [?:1.8.0_141] at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758) [?:1.8.0_141] at java.awt.EventQueue.access$500(EventQueue.java:97) [?:1.8.0_141] at java.awt.EventQueue$3.run(EventQueue.java:709) [?:1.8.0_141] at java.awt.EventQueue$3.run(EventQueue.java:703) [?:1.8.0_141] at java.security.AccessController.doPrivileged(Native Method) [?:1.8.0_141] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) [?:1.8.0_141] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90) [?:1.8.0_141] at java.awt.EventQueue$4.run(EventQueue.java:731) [?:1.8.0_141] at java.awt.EventQueue$4.run(EventQueue.java:729) [?:1.8.0_141] at java.security.AccessController.doPrivileged(Native Method) [?:1.8.0_141] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) [?:1.8.0_141] at java.awt.EventQueue.dispatchEvent(EventQueue.java:728) [?:1.8.0_141] at org.GNOME.Accessibility.AtkWrapper$5.dispatchEvent(AtkWrapper.java:700) [java-atk-wrapper.jar:?] at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) [?:1.8.0_141] at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) [?:1.8.0_141] at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) [?:1.8.0_141] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) [?:1.8.0_141] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) [?:1.8.0_141] at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) [?:1.8.0_141]

with the final message:
Error message: (Not all) required Open Office jars were found inside the installation path.

my java version:
openjdk version "1.8.0_141"
OpenJDK Runtime Environment (build 1.8.0_141-8u141-b15-1~deb9u1-b15)
OpenJDK 64-Bit Server VM (build 25.141-b15, mixed mode)
libreoffice-java-common package is installed.

Evidently Jabref is looking for those jars in /opt/openoffice4, which never existed on my computer, and keeps doing this although I selected the correct paths during manual connect.
Resetting the preferences did not work for me, neither did importing the preferences of the 3.8.2 version into version 4.0.

In previous versions it really helped that the error message contained the information in which folders Jabref was looking for the files.

Thank you.