hi!,
some checks...
On Guacamole:
1) "connection to srv-winXXX", try it with ip's for debug
2) "connection to srv-winXXX" try security with: any, nla, tls, etc
3) tree a connection from guacamole to a win10 client too !
4) check for rdp port 3389 !
On Windows Side ...
check if ...
Windows...