Need help with the game

[Sadman]

Hello,
I've stuck in the story plot mode. After the Capitol attack i cannot move forvard with main missions, because I have to kill The Hornet guy in Tidal Basin. I see it on the map but it's unaccesible. I'm over 40 lvl but it steel displays in grey. Switching between 'game mode' seems not to work in the second mode it switches to red skull and says that I have to kill The Jupiter guy. I've done it but it's steel locked. I'm kind of frustrated, trying to solve it since couple weeks.
Can anyone help me how to unlock this?
I keep walking around the map, Does my character have to meet any specific conditions?
Thanks in advance.

[... Sadness.exe]

To complete the invasion and enter Tidal Basin, you need to: complete 3 operations that are captured by the Black Tusk (they are displayed in red and with the Tusk icon), after that, the Stronghold captured by the Black Tusk will open (also displayed in red and with the Tusk icon). And only after you complete 3 captured operations and the Stronghold - the entrance to Tidal Basin will open, after passing which, the invasion stage will be completed.

Notes:
• The locations of the captured operations and the Stronghold change every week.
• If the icon is grayed out (displayed in gray, it happens), simply change the difficulty back and forth to activate the replay.

[Sadman]

Thank you for your answer. Indeed, I changed the difficulty of the world to a higher one, then to a lower one, and a new mission appeared. Then I did the tasks one by one, National Zoo, The Pentagon etc. However, although I did the missions around the map and outside it, I don't really know if I finished the story or not. I was hoping that at the end there would be some animation with the final letters or something. And here, in fact, there was an animation from each mission like National Zoo or Pentagon, and I don't really know if I did them in the right order. I just finished them. Now I have completed all the main missions and fortresses on the map. But there are still enemy checkpoints and Black Tusk is still in the city. And honestly, I don't know if this is the end or not? It's very confusing :/ But thank You for Your help anyway.