Both the 800 controllers and the maximum supporting ArubaOS 5.0 are end-of-support for some time now. You can't generate licenses in the MyNetworking portal for that reason.
You may try to contact Aruba TAC if they can and are willing to generate a license, or contact your local Aruba SE if he/she can do something for you in this case.
Please be aware that because the firmware is end-of-support for some time, it will have known vulnerabilities and it is explicitly not recommended to run such a solution.