When connecting to your PWA via Project Professional you get the error message: "Could not retrieve server initialization data"
Here is how to solve the problem.
1. in Internet Explorer, make sure your PWA is listed in your list of Trusted Site
2. Since you may use different credentials to connect to different PWA, In IE Security Settings, make sure you have selected the option:
"Prompt for user name and password" as per the screenshot attached.
3. Exit IE and Project Professional
4. Open Project Professional again and connect to your PWA
5. When prompted, enter your credentials.