use it ar ur own risk (the older one) but if done properly, the 99 downgraders are made to downgrade from "atleast" Rebug 4.30.1, as i never run'd this i can't 100% make a claim....u run it from system-update? u have qa flag enabled?(hover over Network settings and do the button combo" u get edy viewer etc...then enable "system debug update" to ON, try again, make sure the rebug spoofer isn't enabled, although should not matter for the "999_downgrader" .. fail again? then drop the PUP into "hdd0\updater\01(folder) and drop the PUP in folder "01" make sure u have debug settings: System debug update ON
then try to downgrade from XMB - system update - internal HDD, all this works fine on 4.21.2
edit: some extra info, the updated 999 downgrader should work, old is removed, updated one(3.55.4) is fixed and waste of time trying?...
check this Rebug info...HOWTO downgrade from 4.21.2/4.30.1 etc..)
it could even use the "normal" 3.55.4 if the PS3 is qa flagged, else use the 999 one
From XMB REBUG 4.21.x AND HIGHER can be uninstalled with the same or higher firmware version OFW/CFW/MFW or with REBUG 3.55.x REX EDITION on a QA enabled PS3 or with the ’999′ DOWNGRADER if QA was NOT enabled
REBUG ’999′ DOWNGRADER
THIS WILL SET YOUR SYSCON COREOS VERSION TO 9.99 ON PURPOSE: DO NOT PANIC
REQUIRES SYSCON DEHASHING AFTER DOWNGRADE
From XMB install ’999′ DOWNGRADER over any firmware version CFW/MFW with spkg sig check patched on a PS3 with or without QA enabled.
UNINSTALL/DEHASH: REQUIRES PS3 TO BE QA ENABLED
From XMB ’999′ DOWNGRADER can be uninstalled/dehashed with the REBUG 3.55.x REX EDITION or from Recovery Mode with any other 3.55 OFW/CFW/MFW.