Trying to install Phoenix but told I have not installed Hex

I have a problem when i try install phoenix.
I get clean system - debian, when i put:
mix archive.install hex phx_new 1.4.0
I got info about not installed hex - select YES (install hex) and instlation is stuck. Nothing happend. Any idea why?

It has access to the internet and that’s tested sans proxy (or otherwise specifying proxy info)?