The reasons for this situation are as follows:

1. Network problem: Car music requires network support to play normally. If the network signal at the location of the vehicle is poor or the network connection is unstable, the car music may not be played.

2. Vehicle system failure: The vehicle system may malfunction, resulting in the inability to connect to the network normally. For example, a damaged network module or wiring problem in the vehicle system may result in no network connection.

3. The data card is in arrears: If the data card of the vehicle system is in arrears, it may also lead to no network connection.