Cannot connect to the docker daemon when running rancher/agent

I’ve got Rancher v2.0.0 running in an Ubuntu 18.04 VM but I’ve recently had this issue: everything’s marked as available but I can’t do anything with it. I think from what I’ve read that it’s because I only have one node. The VM currently has everything on it. I created a separate Ubuntu 18.04 VM to be used as another node. I installed Docker on it but I get ‘cannot connect to the docker daemon’ when I try to run the rancher/agent image. Other agents run without issue so I don’t think it’s the Docker install.
I’ve wasted a lot of time with this issue already so would appreciate any input.