There are two common scenarios for not seeing a project in the xView - please check if some of both is applied:
The most probable one is the project not to have a current iteration (iterations that are already ended or not started are not shown in the xView dashboard) (You can check in the TeamPulse application -> Planning -> View Schedule).
The second one is your user not to have permissions to see the particular project. Please check that by opening the project in the TeamPulse application -> Settings tab -> "Project Members" and "xView Settings" screens. (If that is the case you will need to use another account that is a project member.) (See the two screenshots for example.) Your user should have at least "xView Access" permission.
I hope that helps. If not - please send us screenshots of the two screens mentioned (Settings tab -> "Project Members" and "xView Settings") for some of the old projects that are not visible in the xView dashboard.
the Telerik team