Render Engine not seeing project

Hi there,

I've set up AE6 Render Engine on 5 machines, did some testing with one project and all went fine. Different project set up and tested again, this time however one machine wouldn't start rendering, just stuck in a loop of watching the watch folder. 4 machines started rendering fine, then one errored on a frame and now won't start rendering again. All computers have same plugins and fonts etc. Any ideas as to why a machine would start a render on one project but not on another?

R