I was not selecting Neptune originally, but I was able to travel there and start the quest, which shows that I do have access to the content... I occasionally get this notice when trying to access things from the Destinations map, https://imgur.com/nlxdIlp . I am experimenting as I write this reply. I went to The Tower then when I clicked back on Neptune it popped that up again. I exited the menu and went back in and it worked again..? I wasn't receiving any errors, just that pop up in the link and unable to proceed past it each time. I feel like I'm going crazy because it is working most the time now as of writing this.