With Remmina everything works perfectly, but with KRDC when I click right connect then there is no return message that display why the connection was not possible. Even xfreerdp works fine.
I use Kubuntu 19.10-64bits.

About 2-3 years ago I also had connection problems to Windows 7 hosts and switched to xfreerdp. I cheched even quickly krdc (ver. 4.14.16) and sucessfuly connected to win7 and win10 hosts. If you integrate xfreerdp in you KDE menu, it does not difference what tool you use.