The file which is created to make FMCB possible, is (MagicGate-)encrypted.
The encryption relies in one part also on the MemoryCard-Hardware-ID (every Sony-PS2-MC has a unique ["burned"] ID, similar to Ethernet-/LAN-Cards...).
That´s why you can´t copy the file straigt over to another MC.
Also the "Signing-ID" for FMCB (the complete generated Key for decrypting, also called "MCID" in the Homebrew-Scene/FreeVast-/FMCB-Project), differs for different PS2-region.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux