What is reasons why his phone is off?

As an AI language model, I don't have any context about a particular person. However, here are some general reasons why someone's phone could be off:

1. Battery: If the battery of the phone has drained completely or is faulty, the phone will not turn on.

2. Maintenance: Regular maintenance of the phone is important, so if the phone has not been maintained properly it can cause the phone to switch off.

3. Software or hardware issues: If the phone's software or hardware is not working properly or has been damaged, it can cause the phone to switch off.

4. Overheating: If the phone becomes too hot, it can switch off to prevent damage.

5. Water damage: Exposure to water can damage the phone's internal components and cause it to switch off.

6. Settings: If the phone's settings are not configured properly it may cause the phone to switch off.

7. Aging: Over time, the phone's components may start to wear out and cause it to switch off.

In summary, there are several reasons why a phone may not turn on or switch off suddenly.