Ensure 445 Windows Shares port is opened.
It appears that despite WMI sessions working, there is a problem when connecting to the machine using the SAMBA protocol. The port for SAMBA is 445 so you will want to check if the machines can communicate over that port.
A way to test this is to try copying/deploying a file from the NMS host to one of the target machines and using Powershell to verify if the connection was established.
In Powershell you should see the following:
?? PS C:\Users\berch11> netstat.exe -an | ? {$_ -match "445"}
TCP 0.0.0.0:445 0.0.0.0:0 LISTENING
TCP 138.42.234.219:60720 138.42.229.66:445 ESTABLISHED
The second IP address in the highlighted portion is the machine that I have connected to and communicating with over port 445.