I have downloaded the plugin for trial. Trial time expired. I bought the plugin and uninstalled the trail version and installed a new one. I opened the Realtime software, and no option to insert a Serial Key Number!
 There is just an option to Close software, endless retry button, and a link to re-BUY....
How can I insert my Serial Number??
, 

I had the same problem - the instructions for license activation were in a subsequent eMail from RL.

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Software developer. iClone hobbyist since January 11, 2020. Best work so far: Robots among us: The Lab and The sad end of a legend
In progress: Black Mamba
AMD Ryzen 3950X 16C/32T 4.2 GHz, 64GB RAM, RTX2080 11GB, 2TB Samsung 970 Pro SSD, 8TB Seagate BarraCuda HDD, Win11 64-bit, iClone 8.12