Where to look for the key
BitLocker (Windows). The recovery key is a 48-digit number. Windows usually saves it to the Microsoft account used on the computer, or to the work or school account if the computer belongs to an employer. Some people also printed it or saved it to a USB stick when encryption was switched on.
FileVault (Mac). The login password of a user on that Mac unlocks the disk. A recovery key may also have been shown when FileVault was turned on, or kept by your employer if it manages the Mac.
What to tell us
In the enquiry form, say whether the drive asks for a BitLocker key, a FileVault password or something else, but do not type the key itself into the form. If the key cannot be found, we tell you before any paid work starts, because recovering more locked data would not give you files you can open.