I remember years ago when a friend was looking for a job and inquiry after inquiry resulted in no response. It was a discouraging episode in this friend's life, but one that finally resulted in a number of good responses and a good job.
To inquire again and again and get no response is frustrating at best. What do you do when that happens?
First, figure out if the addresses you are using are correct and if the person you are contacting is receiving the message. Sometimes, messages get lost.
Next, inquire as to why you have received no response. Often there is a good explanation.
After that, consider the contents of your inquiry, and try again with a different approach. And consider having someone who is connected to the person or organization you are trying to contact be an intermediary for you.
And finally, reflect on the fact that the individual or organization may simply not want to contact you. Don't take it personally as there are many reasons why people don't respond, but do try to figure out what a lack of a response may mean. Then move on.