Can't access the web interface in Hadoop version 3

Question

I'm running Ubuntu 18 in a VMware workstation, and have followed these instructions:

https://www.digitalocean.com/community/tutorials/how-to-install-hadoop-in-stand-alone-mode-on-ubuntu-18-04

It works, but I can't access the web interface on localhost port 9870.

It says:

unable to connect

in Firefox.

I've tried to connect in my navigator to various ports like 5010, it doesn't work.

Hadoop seems to be working and I've formatted the HDFS.

Please help!