Staying close to Grandkids abroad.

My DGS in the USA are now 12 and 17. Although I do not see them or talk to them frequently I still know all their news and if they have something very exciting to tell they will do so via FaceTime. I speak to DS each weekend and at times the boys are ‘passing’ the computer and shout out a greeting or stop and show something etc.
It is hard but as the children get to their teens they do change - I have one DGS and one DGD in U.K. - I am in frequent contact with both of them but I find that DGS will eventually reply to any message or email I send -DGD will often send a one liner just as she would say something in passing. They are both in their 20s.

I am sorry your gcs are so far away. I think at 11 things change and its going to be more difficult so hope that you may get some helpful suggestions on here.
My advice for what its worth is to keep trying to keep a relationship going. Perhaps speak with the parents to see if they can advise.