Hm. Perhaps it's just hard to say from here what exactly is the problem until we see that with our own eyes. Are you available for a support session? We could connect to your Viewer PC (just install the Host on it) and then try to diagnose the issue by trying to connect from your Viewer to the Windows 8.1 Host.
Please, send a message to firstname.lastname@example.org and let us know what date and time is suitable for a remote session. Thanks!