I had Multiplicity running on my home computer, connecting to my work laptop--both on my desk. Both running on the same Wifi using "Private" settings.

My home computer got a nasty virus, which migrated to my work laptop when I tried to use a thumb drive to reinstall Windows on my Home.

About that time, we got an over-zealous new IT guy at work, who made a bunch of changes to our security, some of which, he didn't understand the ramifications of.

Long story short, when I got everything rebuilt, I could no longer connect to my work computer using Multiplicity. Couldn't even ping my laptop, which told me right there it was a Firewall issue.

I am an "Admin" on my laptop but it wouldn't let me allow any program exceptions on Windows Firewall. I kept telling my IT guy the issue was a Group Policy issue but he either didn't believe me or didn't care to fix it.

Two days later, after much digging around various possible fixes online, I stumbled onto making a policy exception on my local computer, which you can do if you're an admin EVEN IF there's an overriding Group Policy at the Enterprise level.

But first, to do that, I tried running "Group Policy Editor" on my laptop, but it wouldn't run without the Remote Server Administration Tools, which I installed. Then installed, "Group Policy Editor." 

Once that was installed, all it took was this simple change and voila! Hope this saves someone else a ton of time.