For me was the same and could not made them.. I think if you turn off and then back on again your pc the Exception rule of the firewall will need to be done again. If you do not have a rule made in the firewall for the xc app with forwarding port 32348 I would make it If you already have I would disable it and enable it again..

After doing so I can now make 1 to 2 xcs private transactions..I cannot hoever made larger numbers of xc transaction so there might be bugs still or there might be some settings I'm not aware of that you and I made wrong...

Im waiting for an official guide on how to set up a mixer too