I installed the database replication module (and the MxModelReflection module, as a dependency) into my project and connected successfully to a database I wish to import from, and when I try to create table mappings I can see all the tables in the import source database. But when I bring up the selector for a model object (module and type) there's nothing in the list so I can't connect the source table to the corresponding type in my model. The list should be full of Mendix object types I assume, being all the types available in the model of the currently running application, right? But it's empty.
Did you configure the MxModuleReflection? See its documentation in the app store, section Configuration.
If the MxModuleReflection has been properly configured, do you see your objects in the MxObjects_Overview form (located in the module MxModelReflection, folder General)?