I've had a similar experience, where the drive shows as locked, but selecting the drive reports the error "The drive protected by Bitlocker is already unlocked". After a small amount of experimentation, it appears that the Explorer shell is a little confused and shows the drive as locked when it isn't.
The result of the confusion is that Explorer sets "Unlock Drive" as the default action for the drive, rather than the usual "Open"; selecting the drive in the folder list on the left, or double-clicking it, will attempt the unnecessary "Unlock Drive" action.
Whilst Explorer is in the state, however, you can right-click the drive, and select "Open" and it will then happily show you the contents of the drive (even though it still thinks its locked). Alternatively, you can use Task Manager to kill
explorer.exe and then start a new instance of it - the newly instantiated Explorer should show the drive correctly as Unlocked and allow you to interact with it as normal.