.net Could not load type 'Sendbird.Chat.SbInitParams'

I’ve download and installed the Sendbird.Chat; package and on initialization I keep getting the following error

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.TypeLoadException: Could not load type ‘Sendbird.Chat.SbInitParams’ from assembly ‘SendBirdChat, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null’.
at SendBirdChat.Form1.<toolStripButtonConnect_Click>d__4.MoveNext()
at System.Runtime.CompilerServices.AsyncVoidMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
at SendBirdChat.Form1.toolStripButtonConnect_Click(Object sender, EventArgs e)
at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)
at System.Windows.Forms.ToolStripButton.OnClick(EventArgs e)
at System.Windows.Forms.ToolStripItem.HandleClick(EventArgs e)
at System.Windows.Forms.ToolStripItem.HandleMouseUp(MouseEventArgs e)
at System.Windows.Forms.ToolStripItem.FireEventInteractive(EventArgs e, ToolStripItemEventType met)
at System.Windows.Forms.ToolStripItem.FireEvent(EventArgs e, ToolStripItemEventType met)
at System.Windows.Forms.ToolStrip.OnMouseUp(MouseEventArgs mea)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ToolStrip.WndProc(Message& m)
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)

not sure what I’m doing wrong but it’s the first line in the program which crashes

            SendbirdChat.Init(new SbInitParams("xxxxxx-BC11-4851-B53E-A22F2A4E9F01"));

Any help will be gratefully apprecaited