Difficulty uploading a json file

Hi,

I’ve been trying to post a comment on a post that’s marked as “solved” and I want to attach a json file to it. It gives me an error:

This is my first time running into this problem. What could be the cause?

The json are a few mappings from a CSS script. This is the post I wanted to leave my comment on.

I took an attempt at solving OP’s request; I’m not sure if he still needs or wants it but I figured other people might find it useful so I still want to post it.