How about providing a link to the ad and indicating which button, exactly, you are clicking on? But more than likely, Elena is correct.
Quire frankly, some advertisers do need to manage their accounts here a bit more effectively if they expect to get replies to the ads they place on this site. I have to chase after members quite often who no longer have valid email addresses, or such as in this case, allow their private message inbox to fill up and reject new messages from prospective customers.
I guess you know the old adage, "You can lead a horse to water, but you can't make them drink."
Well, sometimes that does apply here.