Hello,
I've been going for the chartered company achievement in my playthrough and I seem to have met the requirements, but the achievement didn't unlock for me.
I reached the investor tier without having used any trade routes other than charter routes and that didn't seem to do the trick.
There was talk elsewhere of other, hidden requirements, such as making investors happy or having 3,000 engineers and building a bank, but neither of those unlocked the achievement for me either.
I'm not the quickest player and it did take me quite a long time at this point, so I would appreciate any help that I can get.
Here's a link to what I think (?) are the relevant savefiles: https://file.io/k3ItzgRNnWhv
Thanks