chances are there will be no compatiability until windows 10 comes out of preview beta mode.they are working on things but you havve to understand what your playing with is not the final windows 10.its a prototype.that being said it takes alot of resources and money to perfect these addons and updates and i doubt they want to waste money on things that may not work in the official release.thats just my view on it
Multiplicity should be working just fine with Windows 10. There was an issue with KVM mode in the early preview builds of Windows 10, but Microsoft fixed their bug and it is all now functional again.
I imagine in this case it is a networking thing. I would check the IP address of the secondary and see if it is in the same subnet (based on 255.255.255.0 as the mask), as by default it would be blocked otherwise. Also check the network on the secondary is set to home or work vs public as the default firewall settings will block Multiplicity on a public network for security reasons.
