Are you on a phone? Pad? Laptop/desktop?
Phones and pads cannot display chat because support for Adobe Flash was removed from phones years ago. If you're on an Android phone or tablet there is a chat app in the Google store.
If you're on a pc or laptop make sure your Adobe Flash is installed and up to date. If that doesn't work try a different browser. If still nothing look through the other threads up in this subject to see if answers have already been given for your particular problem.