The author made this answer to a user who was desperate not being able to update his theme:
We are back to start updating our themes since ENvato have upgraded its criteria to accept updates the reasons it is time taking and you will see a huge update very soon from now onwards. We are committed to provide free support to the update awaiting clients as well. Thank you > Blockquote
So will Envato be able to push an author to update their theme - in this case, the theme hasn’t been updated since 2016, and now everybody is stuck with PHP 5.6 - so nearly no plug-in updates without crashing ones site. The author is still selling the theme.
My personal opinion as an author is that outdated WP themes which do not work on the latest WP version and with the latest PHP should be removed. But I am just an author here, I don’t have any power over such decisions.
I do not think that Envato Help would be able to do anything with it right now. If the theme explicitly sates which versions it supports and it works on those versions then technically is everything alright, even though it doesn’t make any sense to sell outdated themes.
I guess that your best bet is to switch to a different theme by an author which keeps all his portfolio up to date (for example my oldest theme is from 2014 and I still keep it up to date).