When trying to install PSP Custom Firmware 6.20 over a 5.03-GEN my psp goes into a brick.

I tried to unbrick with pandora and MMS (DespertarCementerioCFplusv8), but it is not working. No recovery menu, no screen at all, only the green bricked light on the power led.

Tried the pandora/MMS with other psp and it works like a charm. The recovery menu appears.

Any ideas in how to revive this?

Thanks in advance.