Display variables

I am taking a pen testing course. We are using proxychains. When I do the command from the course “proxychains firefox google.com” it gives an error of “display variables not set” I have tried to set these but cannot figure it out. I dont know the exact variable it is wanting. Any help in this would be greatly appreciated.

I deleted the Kali VM i had and started it new. Same issue but this time i have not tried to edit variables yet. So I looked at what the variable is now and it is set to :0.0

Well i fixed it. The first time i exported settings I did it after trying something that was wrong. This time iI exported :0.0 and error went away.