How should I react to such a person?

So a friend told me I should contact him via WhatsApp once I've settled in.

After about a month, I wrote to him and briefly described how everything was.

So, I wrote him this three days ago. He read the message but didn't reply.

So I waited and posted something in my status. He looked at it, but there was no response. So if he didn't have time to reply, he probably wouldn't have read my message and status, or he could have let me know he'd reply later.

He's never done anything like this before and I'm kind of sad because he's never done anything like this before.

Sure, maybe something is going on or something, but he's constantly online and sees my status, etc.

So how should I react?