You know nothing about the situation. Have you ever tried booking a tour? How about a tour in a foreign country? Tours are booked months in advance and circumstances can unfortunately change. If it was a possibility for them to come over, they would have.
The only reason they didn't get in last time is because they didn't have work visa's. So that is pretty much the fault of someone, I mean how can you not know to have that. Did someone not mention it along the way? The reasons this time are that the member changes leave them in a place where a new member won't know the songs so they don't feel right touring so quickly with a new member from what I gather.