You should do this in CEX mode.
Here is an extract of the XMB CFW Settings Readme by mysis:
=BD Remarry=
1) Toggle Factory Service Mode (should be easy now in Network->cfw-settings->Toggle Factory Service Mode)
2) Put "eid_root_key" that belongs to the console to /dev_usb/
3) Select Remarry Bluray Drive in Network->cfw-settings->Remarry Bluray Drive
4) If everything went fine it should have notified: "CEX_drive_init() succeeded"
5) Get out of FSM
6) Dont forget to repair CRL/DRL if you need to fix it to play BD videos, try the multiman method first!
Successfully remarried /dev_usb/cfw-settings.log should look like:
2011-12-31 19:00:24 [xai_plugin] : : _xai_plugin_prx_entry()
2011-12-31 19:00:24 [xai_plugin] : 1 : xai_plugin_init()
2011-12-31 19:00:24 [xai_plugin] : 1 : xai_plugin_start()
2011-12-31 19:00:24 [xai_plugin] : ACT0 : xai_plugin_action(remarry_bd)
Looking for lv1 offset
Found lv1 code @0xac574
EID2 P-Block decrypted
EID2 S-Block decrypted
sys_storage_open(bdvd) = 0
stg BDVD Auto Request Sense OFF success = 0
Identified Drive = SONY PS-SYSTEM 302R4154
ps3rom_lv2_mode_select(2) = 0
ps3rom_lv2_write_buffer(2,60) = 0
ps3rom_lv2_mode_select(3) = 0
ps3rom_lv2_write_buffer(3,670) = 0
ps3rom_lv2_mode_select(4) = 0
ps3rom_lv2_write_buffer(4,8000) = 0
CEX_drive_init() succeeded
2011-12-31 19:01:20 [xai_plugin] : ACT0 : xai_plugin_action(service_mode)
Product Mode Disabled