Hi, and welcome.
Wow, you’ve certainly tried hard. I don’t admit this often, but I develop sites on Godaddy quite frequently - I dislike them, but my clients use them.

Though I’m not a huge fan of Godaddy support, I will say that there’s no way they can be experts on all the zillions of scripts people install there.
I’ve never had any trouble with TinyMCE on Godummy, er, Godaddy.
You said that Godaddy installed it. A canned install? I have never tried this, I always install the whole thing myself, in case that helps. I also always choose the newer version of MySQL when creating the database - it gives you that choice when you manually set one up. Database installs are a pain there, but they basically work. Maybe that’s why they offer script full installs.
Something to check in Manager: Elements... Manage Elements... Plugins. Do you see TinyMCE there, and is it enabled (no line through it, not greyed out)? If not, then that would kill it.
You mentioned the path to CSS stuff. Right under that, do you see any Tiny options? If not, indeed, it’s not operational. You should also be seeing a dropdown, Editor to Use, that would allow Tiny to be selected if it’s operational.
Hope that helps,
Dave