harmonyOS4.2 can receive events when connect with USB，and cant receive events when disconnect with USB, WHY?

Hi, all

I've met an issue very strange： my phone is Huawei Nova 9 with HarmonyOS 4.2, and I use eventBus in my APP to transfer events from an Activity to a Service in the APP，and all the two components have already registered to the default eventBus.

When the phone connect to my macbook pro wiith USB-wire , then all events come from eventBus can received and handle perfectly, but when I disconnnect the USB -wire from the macbook pro, the service could not receive any events. WHY?