Some deals take a very long time to finalize. I have had acquisition and sale negotiations that have gone on for years. Some deals get done and others die on the vine. If you don’t receive a response to an email you sent to a contact at a company, it is a good idea to check LinkedIn to see if they still work there.
I have been involved in many long term negotiations to buy domain names. Oftentimes, the domain name is not being used, so I follow-up every year or so to inquire if anything has changed. If the person with whom I am communicating has left the company, usually there will be some sort of email deliverability notice indicating an email address doesn’t function. This is not always the case. Here’s one such example.