Why can't I chat privately with people who are not friends in QQ group and send messages?

Under normal circumstances, you can directly click on the group members' avatars or right-click to choose to send messages in QQ group.

You can chat with him/her in private. If you can't chat privately, or you can't receive private chat information, there may be something wrong with QQ software. At this time, you need to download and install QQ again.