Saving my composition with one track using midi guitar 2

When I make a composition where one audio track in Cubase using midi guitar 2 it’s impossible to downnload it after being saved and impossible to export the composition in MP3 format in Cubase

Sorry, I do this all the time, it is possible. Can you provide some screen shots of the routing in Cubase and your MG2 setup?

You might play a softsynth via MG2 that is not recorded and what is not in Cubase can’t be rendered.