Just to clarify. Did you add all your licenses (vCenter Server, and the ESXi licenses) to the vCenter Server's license inventory?
Does the vCenter Server itself has a license assigned?
Maybe some screenshots (with the license key grayed out) may help to understand this better.
What about the "HOSTS" tab. Does it list your ESXi/CPU licenses?
If you add an ESXi host which has already assigned a paid license (Standard, Enterprise Plus, etc) assigned, the Add Host process should automatically add taht license to the vCenter Server's inventory.