Hi Nigel,
If you are using Sentinel LDK 7.8, SL licenses can be generated using "Sentinel EMS" or "LDK LicGen APIs" (also available through the utility "Toolbox").
But generation of a SL License, is only possible if your Sentinel LDK Masterkey is holding a valid Feature "2" (Time Period not expired) and a Feature "3" with at least 1 execution available.
Regards,
Olivier