I started playing City of Abandoned ships. I created a character (the French guy with a scarf on his face). In the first city, I go to the shop (using the fast travel menu) and I try to sell/buy goods. When I click on the arrows to buy or sell a specific good, nothing happens, the counter doesn't go up or down. Writing a number also doesn't work.
I've even tried throwing away my cargo, in order to make space on my ship, but it didn't work. I've tried all kinds of different goods (import, export and contraband). Nothing.

What am I doing wrong?

I'm using the Gentlemen of Fortune mod.