Today, after installing the December 2011 Project Server 2010 Cumulative Update and hotfix, I got the following error when trying to connect to Project Server Web Application:
“Project Web App cannot connect to Project Server”
After investigating the problem, I found this message in the Event Viewer:
“There is a compatibility range mismatch between the Web server and database "ProjectServer_Published", and connections to the data have been blocked to due to this incompatibility. This can happen when a content database has not been upgraded to be within the compatibility range of the Web server, or if the database has been upgraded to a higher level than the web server. The Web server and the database must be upgraded to the same version and build level to return to compatibility range”
To solve the issue I ran the Sharepoint 2010 Products Configuration Wizard and now I’m able to connect to Project Server Web App again.