How can I change the name of my group chat?

I think permissions can affect what you can do in group chats. Since you mentioned you're the owner, you should usually have full control. Double-check if there's any software update available for your iMessage, as these updates can fix bugs and improve functionality.

Another tip is to check if the chat has any restrictions. Sometimes, certain settings can lock certain features. If you still can’t change the name after trying a restart, maybe check Apple’s support site or forums for any known issues with iMessage.

First, make sure you're the owner of the group chat, which it sounds like you are. Sometimes, there can be glitches with iMessage. Try restarting your device and then see if the option to change the name appears. If that doesn't work, consider leaving the group and creating a new one instead.