Where did you buy your PSP? if it is only two weeks old, you may be able to exchange it for a new one, and if they don't, make a lot of ruckus and complain alot and be very loud inside of the store, and they might just swap your brick out for a brand new one
Then you can try downgrading it again!

And hey, if either of those don't work, you could always send the PSP my way I could always use a bricked PSP

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