One of the most frustrating things you will encounter if you submit your DNA to a genealogy site is, contacting your DNA matches. Why? Because people often let their accounts expire and never bother to log in again to check their messages. I don't think a lot of people realize that even with an expired account, you can still check and reply to messages. You can't initiate a conversation, but you can still log in and reply.
Another reason you may not get a response could be because your DNA match is no longer alive. Ancestry.com has been around for over twenty years. Many of the accounts I deal with involve DNA matches who died years ago. If you're lucky, they will have a family member who is still able to access the account.
The most annoying reason for no response would be because some users just don't like their families being investigated. This always surprises me because if your DNA matches are visible on a website, you should want, and expect, people to contact you. Making contact is what it's all about. There's nothing more frustrating than seeing that your message has been read, but didn't get a response. You might also experience a DNA match who doesn't believe anything you tell them. Remember, some people have no understanding of DNA. I've actually had people say "I have lots of people on my match list, but I'm not sure they are really related." Believe me, they are related.
Another problem is, some people actually believe it's a scam if you contact them. As if you're trying to somehow use their family history to collect data or something. That's a bit ridiculous since the data is already available on the website anyway. If you're not willing to chat, you really shouldn't be putting your DNA data online. You can choose to make your DNA data private if you want to. If you're trying to avoid contact, that might be the way to go.
So, what can you do if you're not getting a good response? Or, maybe you just don't know what to say. This is where having someone like myself get involved can really help. I have a lot of experience contacting people. I find that explaining the DNA and what you already know about the families they match to is a good way to break the ice. Instead of ASKING them to provide you with information, instead, TELL them what you know or think you know. Or, if you're confused about something, try saying something like, "Help me understand this."
It's also not a good idea to write too much. Writing a ten-page message about your whole family history will likely scare them off. Save the details for later. Start slow and get them chatting. Again, if they don't believe you are related, ask for help understanding the relationship. Feel free to ask for my help too. I've contacted thousands of people and explained DNA data. If they have a high DNA match to you, it will be hard for them to dispute the relationship. Understanding DNA relationships can really come in handy in these situations.
What about contacting birth parents? This is a bit different than contacting a cousin or distant relative of course. Every situation is different. Perhaps it's a father who never knew you existed. Maybe there was an affair involved. You might want to be careful how you approach it. Find out everything you can about the family before making contact. Think about how your existence might affect other people. I've had people tell me about a variety of responses they've gotten. I've seen many happy endings where the parent was thrilled to be contacted. Other parents completely denied that it was possible or wanted nothing to do with it. The same is true about half siblings. I've connected many people with their half siblings. This often goes really well. People seem to like finding out they had a sibling they didn't know about. Not always though! Some half siblings say "NO WAY! I don't care what the DNA says, my mother didn't have a secret kid." Denying DNA results is a bit silly. You can't change history simply by pretending it never happened. Hopefully you'll have understanding family members. Good luck.
UPDATE - I mentioned earlier that you may have someone on your match list who is deceased. Or, maybe you have a relative who you know has an Ancestry account and they have passed away. Is it possible to get access to their account? I recently contacted Ancestry.com regarding this situation. Surprisingly, yes. You may be able to access their account. There are several rules involved though. For example, let's say your mother had DNA on Ancestry and she passed away and you wanted to access her account. You would have to supply Ancestry with a death certificate and other proof of your relationship. If you find yourself in this situation, contact Ancestry or the company who you submitted DNA to. They may be able to help you.
Next, I'll discuss more on this subject including possible outcomes when you complete your search.