Question on Campaign's Final Islands

[scrapser 11]

I played the campaign and captured all the islands except those that appear around Thermopylae. On one of those islands I captured it. On the other I performed the mission. The other two islands were "offline" so I moved on. When I went back to Thermopylae, nothing happened so I figured I needed to go back to the island I captured and complete the mission there that I had ignored (since I captured it). When I returned I was unable to find the object I needed to complete the mission. The other two islands remained "offline". Did I break the logic or something?