No response from someone IS a response
When a person fails to respond, it's a direct reflection of their interest -- or lack thereof -- in the relationship.
Few things are more aggravating than having to hound a partner, friend, or relative for some sort of reply after we've reached out to them.
Yes, we get busy from time to time, but that doesn't give anyone the right to leave the other person hanging. A terse text with something like "Been busy, will reach out soon" doesn't say much, but at least it shows some effort to bring the other person up to speed on why they've fallen off the radar.
Failing to provide a response for weeks -- if not months -- communicates that you are just not a priority, and that you'll have to wait your turn to get this individual's attention.
This is never the case in a rock-solid relationship, where nothing -- distance, work, kids -- can keep two people from touching base every so often. It's been said that you know a relationship is strong when two individuals can pick up right where they left off the last time they spoke to or saw one another.
As I've noted in recent posts, a relationship is an investment -- of time, of energy, of emotions. When someone fails to do their part, they're showing that they do not care enough to commit such resources. As a result, the relationship suffers because the other person feels like the only one making a conscious effort to keep the relationship afloat.
If the days keep passing and the other person hasn't bothered responding to you, don't harp on it. Move on. Focus on other people and interests in your life. Keep yourself occupied.
Hopefully, he or she will surprise you by coming around sooner or later. But don't hold your breath. Unfortunately, while some people have a penchant for flakiness, others suddenly pop up again when they need something from you.
Don't invest time in anything that isn't bearing any fruit. People make time for the things and people who really matter to them.