What is your (unlocking the SIM or the bootloader)? Are you currently seeing any specific error messages ?

: It is widely used to unlock Sony Xperia phones that are hardlocked to a specific carrier.

: Historically, this was not a free tool. Users had to purchase "credits" (roughly $20–$30) from third-party resellers to perform the unlock.

: If your device's rooting status already says "Bootloader unlock allowed: Yes," you should use the free Official Sony Unlock Service instead. Bootloader Unlock: NO - General - Sailfish OS Forum