Hi Andre,
Thank you so much for the time you spent to help me!
Since I'm using HPE custom image, it might be that the standard free license is not compatible.
So they gave me 2 options:
1. They provided a key which is valid for about 3 years.
2. To be able to apply the free hypervisor license, they asked to use the original VMware hypervisor binaries (instead of HPE custom image).
Thanks again for your help!
YP