try a making a matching game!!!!! Print out pictures of all the grandparents and print off their names they get called, sometimes it’s not just that kids won’t until they want to, sometimes there’s hesitation cause they don’t want to be wrong!
Okay another note to add my mom lives like 15 min away so we see her literally like 10000x a week. So he knows who she is and he knows we call her gran but he just doesn’t care. Lol.
We have a book of photos with all of the key people in my sons life. You could try having one just for Gran and show it to him regularly and also just before he sees her.
Couple ideas that used to make my daughter engage when she was learning how to talk: 1) if Gran will play along (and I recognize this requires putting aside hurt feelings so may not work), she pretends to fall asleep and you guys have to call her name to wake her up. We used to do it with my dad and when I would say his name he would keep snoring loudly and when my daughter would successfully say Pa he would wake up dramatically and make funny faces and my daughter LOVED it. 2) She also used to love it when I would call him the wrong name. I’d be like Look it’s nana! Or call him the dogs name or something. And he would pretend to cry and say, “ that’s not my name! Tell mommy my real name!” Sometimes she would and then he would act dramatically happy again.
Maybe you can introduce him with her picture and also her calling name. Make a book about Gran . He will say it one day. No worries. My son just started saying the word Grandma.