Forward Engineer filters out connections that do not have the same 'Database' name as the database name of the current DbWrench design. The name of the database in the connection definition must match the name of the database in the design. To rename the database, right click on the database node in Database Explorer and select 'Rename' from the popup menu.

Note: You can use 'Save As' to save a database design under any given filename. The filename does not need to match the database name.