Thanks Michel and Fedor. I did as suggested and it workeded for me. See below:
Have you successfully run the 'Read LDAP' function by clicking the button with that label directly under the Server Configuration connection details? This can take a long time to complete if you have a large number of users. It is best to check for errors in the server log until this shows as completed. You must do this before you can complete the other 2 sections. You must make sure your LDAP root directory is correct.
The User Mapping section is used to configure the import of accounts from LDAP (this is all optional). The User Authentication section is used to configure the system to authenticate users through LDAP and can be used with or without configuring the User Mapping section.
Update Have you got a realy small LDAP database you are reading in? Normally there is a log line added after each 10,000 records are read (if I remember right - it was a while ago when I set this up)
When you open the LDAP Server configuration, it runs the microflow OpenLdapServersOverview which runs the java action ReadSystemUserDerivates. This pulls back a list of derivatives of the User entity, and if it fails it should display an error message. So, I don't understand why you do not have a list of entities on the (Select New) field in User Mapping.
When I click on the "Read LDAP" there is a window that pops up briefly displaying the message "Retrieving data from the LDAP Server" then disappears. I receive no errors or confirmation to say that it has failed or has completed.
Also, it states on the module screen "Save the configuration and perform 'Read' before continuing". I cannot save it cause when I try I get a validation message saying "An user entity to define the LDAP -> Mendix mapping must be set!" Shall I try disabling this message. And then saving the settings?