Been having some trouble with the Team Galactic Encounter in Celestic Town. I beat the Galactic Grunt but Cynthia's Grandmother didn't appear and also Cyrus didn't appear. So unfortunately I also can't challenge Hearthome Gym. 

Any solutions how to fix that? 

Hi. Thank you very much for contacting us about your issue.

You see, after you defeat the Galactic Grunt blocking access to the cave in Celestic Town, Cynthia's Grandmother will come to you directly and take the Old Charm Item. Afterwards, you need to go inside the cave and interact with the painting on the wall. Once you do, Cyrus will appear and challenge you to a battle, then you can proceed after the battle.

We hope this information will resolve your issue. Please feel free to ask if you have any future questions, thank you for contacting us and good luck in your adventures!

- Kubrick