Temporarily disable your windows firewall and see if the connections go through. If Swarm is successful with Windows Firewall disabled, there are a couple solutions we can try.
Additionally, on your COORDINATOR machine, you’ll need to make sure your "File and Printer Sharing (Echo Request - ICMPxx) are enabled. (Windows disabled these in a recent Windows update
Finally, on your ALL machines you may need to add a new port rule (8008-8009) to allow Swarm connections through. (Click: “New Rule” → “Port” → TCP / Specific local ports: 8008-8009 → “Allow the connection” → (All Domains should be Checked) → Name it “Swarm Remote Ports”)
It’s possible that your DotNET packages are outdated, or corrupted. Simply run windows update and see if it grabs any missing packages/updates
Option #2: Run the Visual Studio installer and make sure you have DotNET 4.5 Installed
Problem #3: Different Swarm Versions
If you are using multiple machines on your Swarm Network and you want all machines available for rendering, check that you are running the same “Agent Version” as the machine initiating the lighting build. Make sure you use/copy the same files to each machine. The Swarm files are located in (Engine/Binaries/DotNET)