Why would he want me to call him but never respond?

Can someone here pls explain to me why someone (old coworker who I share fond memories with, he trained me and we had a great mentorship) would suddenly call me at work, ask how I am, how im doing at work, asking if I got to this event and town and overall being super nice.. and ending the call by telling me "call me when you get back to (uni) I wanna know what’s next for you". It seemed sincere to me. A few weeks later, I did not call him directly but instead send a quick text message to tell him, that I hope he’s doing well and I’m not sure how we left things, regarding a phone call or something like that, that’s why I’m gonna reach like that for now. Maybes not the smartest message to send, but I still remembered. Why would he decide to not respond to that at all? Does he want me to think that he hates me? The uncertainty makes me really nervous. I thought we had great respect and appreciation for each other. I always felt like he likes me a lot. That’s why it’s so off putting to me. Can anyone help me to understand this behaviour?

Why would he want me to call him but never respond?
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