If you have trouble getting Dreamweaver to connect to a database, and you are pretty sure you have all the settings (username, password, db server, etc.) correct, check out this article

If the host directory path is not quite right, it will not work. It seems that Dreamweaver uploads a hidden file to your host directory. If you have the "host directory" blank or set to the root (not visible to the web) of your server, it will not able to read it. It will give the error "no testing server on server".

There are other reasons given in the article also - but that one is very easy to miss.