I often get people who message me on LinkedIn with an urgent request. I respond immediately and then get no response.
Now you can say they found someone they thought would fit better or they no longer needed you. That’s true. It is also true that when people don’t respond you aren’t inclined to respond to them a second time.
If people waste your time, you don’t have to respond again to them. They have burned the bridge of mutual respect and cooperation.
In the same way if you don’t respond to someone, don’t be surprised if they don’t respond to you. That’s fair isn’t it?