What does it mean that the official account of Chongqing Expressway etc WeChat always shows unbound?

This is normal, and so is mine. It may be that the data of WeChat official account is delayed, or the data on both sides are not connected at all, which leads to this error. In fact, as long as you successfully deduct the fee from your card every time you cross the highway, you don't have to worry, just keep using it.