When you transfer entitlement with move entitlement(View Entitlement page -> Edit -> Copy this Entitlement option) it creates a new activation code.
Solution:
If the requirement is to maintain the same activation code even after transfer, the best solution is to use the converter template.
Details on how to use the converter template is present in community link as below:https://community.flexera.com/t5/FlexNet-Operations-Knowledge/Converter-Template/ta-p/135086
