When you first open a page in dreamweaver after the update, the webassist installer should run. Did that happen?
Then it asks you to restart Dreamweaver when it completes. Did you get this message?
We need a bit more information to determine what is going on here.
I'd first try to reinstall through the extension manager:
1) Open the Extension Manager
2) Close Dreamweaver
3) Uninstall the Extension
4) Re-install the Extension
5) Open Dreamweaver and open a page so that the WebAssist installer runs
6) Close Dreamweaver
If you follow those steps and still have issues, report back here with any error messages you get or any unexpected results you might have in detail and we can look into this with you further.