When trying to connect to another world locally (ie one student sharing their world to another student)  i am getting the following error

P2P error 2147012894

I have whitelisted all addresses. Clients are connecting via auto configuration PAC File, when connecting to the proxy via direct method it works (ie specifying proxy port manually). Something has changed the last few months as it was working without any changes.

Department of Education VIC government school in Australia.