Follow these steps to resolve the problem
StartOpen Commerce Server Manager
Expand CommerceServerManager
Global Resources-->Profiles
Profile Catalog-->Data Sources
For each data source Expand the Data Source and Select the Partitions Tree Item
Right Click on the partitions listed in the right panel and select properties
Press the Test Button to ensure Database connectivity.
Profile Resource Connection Strings
Open Commerce Server Manager
Expand CommerceServerManager-->Global Resources-->Profiles
In the right panel you will see 3 connection strings right click on one and select properties
Press the Modify... button and Test Connection button for the 3 connection string to see if they are correct