Steve, even if you drop the matter, it will come back every so often to haunt you.
How do you know the contact information is current and correct? Did you find him in more than one place and did those places have the same email address? I had a similar problem contacting my subject's half-brother. When I start getting desperate, I look for public mentions of the target and contact them. I even contact the local genealogical society. When that fails, I turn to mailing a post card to the target and anyone else who could help. My library has Reference USA which has white pages. My hand-written message is simple. I am a genealogist researching the family tree of so-and-so. Please contact me. Why a post card? The target is more likely to see the message than if has to open an envelope. The disadvantages are the post office will not return it if undeliverable or forward it. In another search, I had to wait two months to get the target to call me back but he did. Very happy ending.
Next suggestion. The white pages may not work. In the first instance above, I called my lawyer to get the name of his skip tracer. He very nicely checked his Lexis database and called me back an hour later with the phone number I needed. Got my guy. A very happy ending.
Finally, have you used GEDmatch? I prefer this tool but its database is much small than that of Ancestry. However, you get a better idea of the genetics.
Good luck Steve and keep us posted.