Hi there,
I’m having the same issue. Here are running machines and vm1 is the swarm manager:
ubuntu18_10@ubuntu:~$ docker-machine ls
NAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
myvm1 - virtualbox Running tcp://192.168.99.100:2376 v18.09.0
myvm2 - virtualbox Running tcp://192.168.99.102:2376 v18.09.0
myvm3 - virtualbox Running tcp://192.168.99.101:2376 v18.09.0
When I open 192.168.99.100 on Firefox, it displays this:
Seems weird issue 
Edit1: I’ve just found the solution right here:Get Started part 4 connection refused from node on virtual machine - #12 by andreasnilsen . Seems that was due to version of boot2docker.iso