OpenVPN AddOn with RDM 6.6

Hello,
i have Problems with the new RDM 6.6 (Enterprise) and then OpenVPN Addon. My OpenVPN Version is 2.2.1.
When i make the Connect manually it works, but with the RDM VPN and imported Config i get the following Error:

ArgumentNullException - Value cannot be null.
Parameter name: path2

at System.IO.Path.Combine(String path1, String path2)
at RemoteDesktopManager.AddOn.OpenVPNAddOn.OpenVPNAddOn.Open(String parameters)
at Devolutions.RemoteDesktopManager.Business.VPNOpeners.VPNAddOnOpener.Open(Connection connection, VPNConnection vpn)
at Devolutions.RemoteDesktopManager.Managers.VPNManager.OpenVPN(Connection connection)
at Devolutions.RemoteDesktopManager.Managers.ConnectionManager.OpenConnection(Connection connection, OpenConnectionMode openConnectionMode)
at Devolutions.RemoteDesktopManager.Managers.ConnectionManager.OpenConnections(Connection[] connectionList, OpenConnectionMode openConnectionMode)
at Devolutions.RemoteDesktopManager.Managers.ActionManager.OpenConnection(Connection[] currentConnections, OpenConnectionMode openConnectionMode)
at Devolutions.RemoteDesktopManager.Frames.ConnectionViews.FreBaseConnectionView.OpenConnection(Connection[] currentConnections, OpenConnectionMode openConnectionMode)
at Devolutions.RemoteDesktopManager.Frames.ConnectionViews.FreConnectionTreeView.tvList_NodeMouseDoubleClick(Object sender, TreeNodeMouseClickEventArgs e)
at System.Windows.Forms.TreeView.OnNodeMouseDoubleClick(TreeNodeMouseClickEventArgs e)
at System.Windows.Forms.TreeView.WndProc(Message& m)
at Devolutions.RemoteDesktopManager.Controls.TreeViewXP.WndProc(Message& message)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


Greets

Karo