Gazebo not running "No protocol specified"

Hi, I was able to use gazebo in a docker container. At some point now I get the following error when trying to launch gazebo standalone

(I am using Gazebo multi-robot simulator, version 9.13.1 and ROS Melodic with Ubuntu 18.04)

I run gazebo

I get

No Protocol Specified

Then the command exits.

Could you help me understand what is going on?

Asked by desmond13 on 2020-07-08 08:16:59 UTC