Anytime you want to ping/start a chat conversation with someone at work, especially if that other person is up in the corporate ladder, don’t type ‘Hi <name>’ and leave it at that for them to respond.
Such niceties are good for face-to-face conversations but not on chat mediums. Instead, say ‘Hi <name>’, and then proceed to ask/say whatever you wanted to say – the reason why you pinged that other person – (and if needs be) adding that you didn’t want to waste their time, so you’re keeping it short.
You’ll never know in what situation that other person is, so do them a favour by making your conversation short. They’ll appreciate your brevity.
This is a newbie mistake, in general. But most managers will appreciate you being succinct – just don’t overdo or overact. Remember the first law in the book The 48 laws of power – Never Outshine the Master! Although, I don’t subscribe to that thought, it depends on how you stage it. Achieve that balance, and you’ll be fine.
Cheers and good luck!