Create USERMOD license for custom GPU firmware

Hello everyone! I am trying to sign my custom vbios to run on a custom laptop. PMU says it cant execute devinit if i have modded bios, i guess its all because certificate check. I see an option in nvflash:
nvflash64 --licreq=LicenseRequest.bin USER_FW_MOD
but it fails with Error generating license for this request: 7
How can i run my custom vbios on my board? can i override existing keys in my gpu to generate my own cert?