Network Rendering troubleshooting with mixed generation Macs

I am having difficulty getting the network rendering to work in Compressor. I can successfully see all computers on the network, and create a group. All computers are set to allow other computers to process batches from other computers.

When I choose the 'All' group in the Process settings, Compressor does not split the file up, and all computers remain in the 'Idle' status.

Is there any trick to this? The computers on the network are a mix of WIFI and Ethernet networked, and various macOS versions, from 10.11 to 10.14. The Compressor version is the highest possible on each OS, so varies from 4.3.2 to 4.4.1. The machines are a variety of Mac mini, MacBooks, and older MacBook Pros.

I've tried resetting the queue on all computers, but with no luck, so any advice would be appreciated.