I don't know if it's been reported yet, but it seems that Hold+ v4.0 doesn't work correctly.

PS: It's not a very good idea to fuck around with flash0. Trust me on this one. Every time you flash something (ie. from MHU to GEN and back again) you risk bricking it. I have a Fat PSP and even know someone with the same problem. He, on the other hand, had a modchip for his PSP and bricked it AGAIN whithin a year, maybe a year and a half. I'm the lucky one. I only got to brick it once and now I'm on the "Test M33" feature from Despertar Cementerio and still hoping for a Game Decrypter v5.... But that's besides the point.
The point is you shouldn't flash it too many times (for example, when every new version comes out, then you realize it's not so good, so you flash the previous version for a while, then another update and so on).