Cant Decrypt drive C: but drive D: success

Question

Hello All, 
 
 I have an issue harddisk to decrypt, this harddisk OS windows is corrupt. 
 I want to decrypt disk C: and disk D:, I see decrypt code on sophos management and use it to decrypt, 
 
 For disk D: I can use by typing the code but when I want to decrypt disk C: it show popup must plug in the usb to decrypt.

How I can decrypt disk C: because I have my important data on it ?

Thank you.

Jasmin · Accepted Answer

Hi Ari Setiawan 
 If this is the case, I'd suggest you to export the recovery key to the USB drive using this document . 
 After that, you can try the option of "Get the key from a USB flash drive" which will take the key from the USB drive to unlock the drive.