How can I allow friends to boot my server Part Two :o

[ItsAMeNexus]

So, i recently asked for help regarding the above problem, I tested it out with another server first with /join "servername" which worked fine, I tried mine again, 

Reqium.minehut.gg

I only used the Reqium section of the name, and I still receive an error, is there a setting or plugin I need to install to get it to work?

Thanks

[ItsAMeNexus]