Unable to find Gen Application Key for my Device

I am trying to implement FUOTA with the chirpstack-fuota-server.
I am working with this example .
This example needs the parameter GenAppKey and I can’t find this parameter for my device.
I saw that this parameter was in Devices/myDevice/keys(otaa) under the field : Gen Application Key.
But in this tab, I only have the Application Key. (See screenshot)

Is this parameter still available in the application server or is there a new way to acess to the devices with current version?
We are using following versions for our services :
chirpstack-application-server 3.15.0
chirpstack-network-server 3.13.0
chirpstack-gateway-bridge 3.11.0
chirpstack-fuota-server 3.0.0-test.3
Thank you for your kind help