Poor communication with author and issues unresolved

Hi all. First time posting in these forums, but I have been an Envato customer for a long time.

I have a potential issue with an author I bought a WordPress theme from. I won’t name any names because I have sent the guy a message tonight as a last ditch attempt for him to hopefully remember I have outstanding problems.

The long and short of it is I bought his theme 3 months ago, and 1 month of tweaking the theme’s settings and getting certain things to work just right, I launched my website with his theme. There were still a few minor issues, but we went live regardless. Since the very beginning, I noticed his communication was becoming slower and slower. It is now to a point where I haven’t heard from him for 1 month and nearly 2 weeks. Last communication I got from him was on 23rd of April. He has been quite professional WHEN I have gotten communications from him, however, his theme is sold as being responsive, yet it does not show well on mobile devices and I am worried most of my website visitors will be seeing it this way.

What am I to do? Is this the right channel to discuss this? Do I take things up with Envato? I love the theme I bought from him, however it really needs some love responsive-wise.