Hello! I've reached probably the last part of the quest, in which I have to position artillery. I've put 5 cannons along the walls, one for every old platform, but the quest doesb't progress to the point in which the old coot soldier tells me to try them with the flares! Is it bugged? Have I done something wrong?

Please, help!

After building the artillery the quest says to talk to Ronnie. Did you do that? You have to actively talk to her and she will tell you about the fire test.

You have to assign someone to one of the cannons.

The quest doesn't tell me to talk to Ronnie and all the people I meet have the only option to exchange equipment.

Hold V (or equivalent to bring up the workshop menu). Go over to someone, hover over them, and press E (Or equivalent action button). Then go over to a cannon and hit E again. The little guy that you see when you hover over the cannon should turn from red to green. You've now assigned them to the cannon.

Thank you very much!

I did (or didn't do) the same thing. Had to assign someone. But then realized I only had to build one artillery piece, not six.