make sure that you have all the items required for the missions- check in your bag that you have them all and didnt use some of them for another mission/craft already (an example is beer that is used in chapter1 for 2 missions). other than that, from chapter2 onward you cant finish missions in the same day that you got them or if you already had a conversation with the specific captain that day.
you can buy the chapters on itch for 5$ each, or if you become vanir backer (25$) on patreon you can get all the current 7 chapters and their guides, and there are some channels for patreon backers on the discord server.