1. Vehicles do not support this function: some older Volvo models may not have integrated voice control system, so music playback cannot be controlled by voice.
2. Voice recognition problem: If the vehicle supports voice control, but can't recognize the "next" instruction, there may be a problem with the voice recognition system. You can try resetting speech recognition or updating the system to solve the problem.
3. Music playback software problem: If the music playback software used by the vehicle is faulty or incompatible, the voice command may not work normally. You can try to use other music playing software or update the current software version.
If the above solutions are not applicable, it is recommended that you consult Volvo official customer service or automobile manufacturer for further technical support to get a more accurate answer.