Downgraded to 6.20 and can't update to 6.6X

[opedromagico]

Hey people!
I just found my old PSP and I was about to give to my 13y sister to play some psx and psp classics! She loved the idea, but I can't get this to work.. Will you help me out? It means a lot to me and to her.

Here we go:
PSP 3003 - Electric Blue
I was on 6.35 CFW (not permanent)
Formated the SD Card and Restored Default Settings
Downgraded to 6.20 because I thought it was necessary
Now when I try to update to OFW 6.6X:
• Directly: "The update cannot be started. The data is corrupted. (IDXFFFFFFFF)"
• Using Chronoswitch: "Checking firmware... Error, your firmware is not supported."
• Here is a photo: https://drive.google.com/open?id=10CEsqY...p=drive_fs

Any ideas?
Thanks!