Ps3 slim error code 8002F957 ?!

Hi guys ...

I have Ps3 slim and software on it is 4.84 ..
The code of my device is CECH - 2504A ..
So I try to install (REBUG_4.84.1_REX or REBUG_4.84.2_REX) but I have got error code 8002F957 ..

How Can i fix it please ?!
Thank you