Open .SER file in a text editor. Should have the same number inside. If the .SER files are the same you don't new to request a new key. .SER file name change in order to know which product you have when you request and upload to us KEYS.
You can change the Nebula instance in your old projects or rename the new .DLLs as the old Nebula3 names, but just remember to do it all time that you download a new version upgrade.
For example I rename Nebula3CoreII as Nebula3PRO and Nebula3CoreIII as Nebula3PROClient
Enrique Silveti. Acustica Audio customer and technical support.