Only someone who has access to a Xenforo database can work to fix it. Saying that it’s broken, and even exactly how, isn’t enough for anyone to use your information to fix the script.
It’s pretty obvious that the script worked for whoever it was that submitted it and that Xenforo has changed since then.
The set of people on the planet who care about any import script is very, very small, typically only one (or one community) at any given instant. That is, people who care Xenforo don’t care about Discourse, and people who care about Discourse don’t care about Xenforo.
Looks like I last did a Xenforo import in April 2023. Glancing at the diff, it looks like I didn’t do much but change the name of the user(s) table. I see code that does something about attachments and a gallery, and I sort of remember doing something about those attachments, as the site has a bunch of images. As I recall, it was pretty good and the client was very happy with it.
If you’re still working on it and don’t have a budget, I can send you the file in a gist or something.