Illustrator has a very old and annoying bug when using the graph tool: from times to times you can't copy, paste or delete data. Sometimes the keyboard shortcuts stops working and you need to use the menu (slower workflow). But sometimes even the menu doesn't work. Then you need to quit Illustrator and even restart the Mac.

It doesn't matter which OS ou Ai version you have installed. As I said, it has been behaving like that for years.

Please fix it.