I've just installed Synergy 2.0 beta3, and had something similar happen. I'm using (atm) two Windows 10 laptops and a Macbook. The Macbook's screen name does have .local on it. For me, all 3 devices were seen by Synergy. But if the macbook was in the middle, I couldn't reach it with the mouse and keyboard. I shifted the macbook to the left position, and it's working to move between all 3 screens as I expected
I'm sharing this in case it helps narrow down what's happening. I can try to capture the appropriate logs if they'll be helpful.
Thanks!