Freezing Intel/Altera Monitor Programm

Hello,
i have installed like in the documentation.
First i installed Version 18.1, all went well
Then i installed Version 21.1, then i get this problem.

I get also the following message, when i start Monitor_Programm:

OpenJDK 64-Bit Server VM warning: You have loaded library /root/flexdock/RubberBand.so which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.
java.net.ConnectException: Verbindungsaufbau abgelehnt (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:607)
at java.net.Socket.connect(Socket.java:556)
at java.net.Socket.<init>(Socket.java:452)
at java.net.Socket.<init>(Socket.java:229)
at org.flexdock.docking.drag.outline.x11.Connection.<init>(Connection.java:35)
at org.flexdock.docking.drag.outline.x11.Graphics.create(Graphics.java:49)
at org.flexdock.docking.drag.outline.x11.Graphics.<clinit>(Graphics.java:34)
at org.flexdock.docking.drag.outline.x11.X11RubberBand.<clinit>(X11RubberBand.java:14)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at org.flexdock.util.Utilities.createInstance(Utilities.java:285)
at org.flexdock.docking.drag.effects.EffectsManager.createRubberBand(EffectsManager.java:94)
at org.flexdock.docking.drag.effects.EffectsManager.loadSystemRubberband(EffectsManager.java:137)
at org.flexdock.docking.drag.effects.EffectsManager.prime(EffectsManager.java:43)
at org.flexdock.docking.drag.effects.EffectsManager.<clinit>(EffectsManager.java:37)
at org.flexdock.docking.drag.DragManager.prime(DragManager.java:42)
at org.flexdock.docking.DockingManager.init(DockingManager.java:137)
at org.flexdock.docking.DockingManager.<clinit>(DockingManager.java:127)
at monitor.ui.UIManager.initDocking(UIManager.java:337)
at monitor.ui.UIManager.init(UIManager.java:160)
at monitor.globals.Globals.init(Globals.java:87)
at monitor.Main.main(Main.java:36)