What version of DW are you using?
What version of the extensions are installed?
Make sure you have the latest version, for Data Bridge, the latest version is 1.2.1
if you have a previous version of the extension installed make sure to uninstall it from the extension manager before installing the newer one.
After installing the extensions, open Dreamweaver, this should start the WebAssist installer. If the WebAssist installer does not start, you may need to open a PHP page to force it to launch.
after the WebAssist installer completes, make sure to restart Dreamweaver.