The Course Selection window only displays courses that can fit within the available storage allocated to the current render server configuration. If the render server has reached its storage limit, additional courses are hidden from the list until enough space becomes available. This behavior is expected and helps prevent installations that would exceed the server's capacity. 

To make the missing course appear: 

1. Remove one or more installed courses that are no longer needed to free up space on the render server. 
2. Refresh or reopen the Course Selection window.
3. The previously hidden course should now appear and be available for installation. 

The list of available courses is dynamic and depends on the current storage capacity of the render server. If a course is missing, it does not necessarily mean it is unavailable, it may simply be hidden because there is not enough free space for it to be installed.