We just had an update to Windows 10 and I also updated NoMachine on the Windows computer. Now every single connection that I try and make from Windows 10 to Linux gives me the error, Error: Host key verification failed. Note that my two Linux boxes can connect to each other without any problems via NoMachine. This is all via the local network.
There is nothing in the C:\Users\my-username\.ssh or C:\Users\my-username\ssh folders. (And yes, I do have it showing hidden files and folders.)
I was able to connect successfully prior to the updates.
Current Versions
NoMachine v6.7.6 (Windows 10 v1903 build 18362.267)
NoMachine v6.7.6 (Kubuntu 18.04, KDE Plasma v5.12.8, KDE Frameworks v5.44.0, Qt v5.9.5, Kernel v4.15.0-58-generic)