At some point, it may be necessary to Terminal Service into your 4D Server to add expansion licenses. When doing so, unless you take over the administrative console session you will get a new, clean session. Without taking over the administrative console session you will not see any 'Associated Products' in the drop down box when trying to add an expansion number. (Help -> Update License -> Online Activation)

Also, please ensure that the user logging into Terminal Services has proper permissions in place. Failure to have proper permissions set up will also result in not seeing an 'Associated Product' in the drop down box.

Please refer to this Tech Tip for more information on connecting to a Console session:

Windows 2003 Server: How to see the 4D Server window via RDC