@p1r473: I'm not sure what you mean by microsd lock. microsd does not have a lock. If it did and was locked you could not copy new books onto your reader either. Maybe your card is defective, or your card reader / SD card adapter / imaging program is faulty.
If you're open to alternatives you could use my Magic Memory Upgrade Mod. It uses only the Kobo itself to upgrade the memory. (You'll have to copy your books back onto it afterwards.)
https://www.mobileread.com/forums/sho...d.php?t=261578