RDM 11.0.5.0 + OpenVPN 2.1.0.0 error

Hello,

newly installed RDM 11.0.5.0 cannot connect / open VPN (plugin OpenVPN 2.1.0.0):
messages are:
Remote Desktop Manager - Could not create temp files for connection.
and then
OpenVPN GUI - Cannot find requested config to autostart: .ovpn

in applicatin log is (only)
System.NullReferenceException: Object reference not set to an instance of an object.
at RemoteDesktopManager.AddOn.OpenVPNAddOn.OpenVPNHelper.Export(OpenVPNConfiguration openvpnConfig, String path, Boolean showResult)

previously used RDM 11.0.4.0 worked

(tried both 32 and 64 bit version, running as Administrator)