What is why is he leaving me on delivered all of a sudden?

If someone is suddenly leaving your messages on "delivered" without responding, there could be several reasons for this, and it's often not easy to pinpoint exactly which one applies without more context. Here are some possibilities to consider:

1. Busy Schedule: They might be preoccupied with work, studies, or personal matters and haven't had the time to respond.

2. Need for Space: Sometimes people need a break from social interactions to focus on themselves. This doesn't necessarily mean anything negative about your relationship.

3. Technology Issues: Technical problems, such as phone issues or app glitches, might be preventing them from noticing or responding to messages.

4. Miscommunication or Misunderstanding: There might have been a misunderstanding or disagreement that hasn't been fully addressed.

5. Loss of Interest: It's possible they've lost interest in the conversation or the relationship in general, leading them to disengage gradually.

6. Overwhelmed by Messages: They could be overwhelmed by the volume of messages they're receiving, especially if they're going through a busy or stressful period.

7. Personal Issues: They may be dealing with personal issues, such as health problems or emotional challenges, which could make it difficult for them to communicate.

If you're concerned or confused about their lack of response, it might be helpful to reach out with a gentle message expressing your feelings. Let them know you're there if they want to talk and give them the space they might need to respond in their own time. Communication is key in understanding their perspective and maintaining a healthy relationship.