Is this on a theme where you are including ACF in the theme? There are some things that ACF does that will never pass Theme Checking, for example, reading local JSON files. Including ACF in a theme and expecting it to pass the theme check plugin is unrealistic.
I’m sure there are others there selling themes that include ACF, maybe ask them what they do? Or ask the people in charge there?
I’m not familiar with Themeforest. I am a little familiar with the theme check plugin and I know some of the things it does not like. The biggest one you’ll have to overcome is the one I mentioned above. The function call for file_get_contents(); throws up a big reg flag in theme check and doing a lot of digging I discovered that there isn’t any way around using that function without completely defeating the purpose of saving fields groups in local JSON files, which is reducing execution time.