Error after Upgrade

I have upgraded my old Manager version with the new one and I am now getting this error

ManagerServer.SerializationException: Exception of type 'ManagerServer.SerializationException' was thrown.
at ManagerServer.Upgrade.Get () <0x01b57>
at ManagerServer.Objects.Get (System.Guid) <0x0067f>
at ManagerServer.HttpApplication..ctor (bool,System.Nullable`1<ManagerServer.Edition>,string) <0x00473>
at Manager.Form.CreateMainForm () <0x0092f>
at Manager.Form/<>c__DisplayClass3.<Show>b__1 (object,System.EventArgs) <0x0001b>
at Eto.Forms.Application.OnInitialized (System.EventArgs) <0x00023>
at Eto.Platform.Mac.Forms.ApplicationHandler.Initialize (MonoMac.AppKit.NSApplicationDelegate) <0x0001f>
at Eto.Platform.Mac.AppDelegate.DidFinishLaunching (MonoMac.Foundation.NSNotification) <0x0004b>
at (wrapper dynamic-method) object.[Eto.Platform.Mac.AppDelegate.Void DidFinishLaunching(MonoMac.Foundation.NSNotification)] (MonoMac.Foundation.NSObject,MonoMac.ObjCRuntime.Selector,MonoMac.Foundation.NSNotification) <0x00033>
at (wrapper native-to-managed) object.[Eto.Platform.Mac.AppDelegate.Void DidFinishLaunching(MonoMac.Foundation.NSNotification)] (MonoMac.Foundation.NSObject,MonoMac.ObjCRuntime.Selector,MonoMac.Foundation.NSNotification) <0x000fb>
at (wrapper managed-to-native) MonoMac.AppKit.NSApplication.NSApplicationMain (int,string[]) <0x00003>
at MonoMac.AppKit.NSApplication.Main (string[]) <0x0003f>
at Eto.Platform.Mac.Forms.ApplicationHandler.Run (string[]) <0x0008b>
at Eto.Forms.Application.Run (string[]) <0x0001c>
at Manager.Form.Show () <0x00115>
at Manager.Program.Main (string[]) <0x0001f>

Could someone tell me how to deal with this?

You are not using the latest version. Maybe you didn’t upgrade properly?

Try to uninstall the program completely, then install again from http://www.manager.io