Here’s a quick post in case anyone else notices a yellow exclamation point on a volume in “My Computer” after installing the fall update (1511 build 10586) for Windows 10.
I did this install on a Surface 3 and it failed a couple of time hanging around 40% complete until I found this link on the Microsoft Answers Forum, that explains an issue installing the update if you have an SD card installed. I did and had to cancel the update a few times, which might be why I had the yellow exclamation point in the first place.
The cause is the drive encryption (BitLocker) which is turned off. BitLocker is used to encrypt the hard drive of the Surface and is on by default. I assume it needed to be turned off during the update and since mine failed a few times, was not turned back on. On a Surface 3, you can’t manage BitLocker settings in Control Panel, because the device comes with Windows 10 Home. So the way to manage this is from a PowerShell prompt.
- In the Cortana search box, type PowerShell
- Right-click on PowerShell and select “Run as Administrator”
The following will open
- Type the following Get-BitLockerVolume
A list of BitLocker volumes will be displayed
Notice the “Protection Status” is off. We want to turn this back on.
- Type the following Resume-BitLocker -MountPoint “C:” (or what ever volume mount point you have listed)
That’s it. The “Protection Status” is now set to “On“. Open up “My computer” and there should be no more yellow exclamation point.
Robert C Mitchell's Blog 
#1 by Luke on August 20, 2018 - 10:53 AM
what if there is 100% encryption on the drive, AutoUnlock – false, Protection Status – OFF.
I moved this drive from another computer and i see there this yellow exclamation mark. In Bit Locker manager it says “Pending Activation”.
I did follow steps to re-enable it with power shell and it poped message in red that says:
“Resume-BitLocker : At least one secure key protector is required for this operation to be performed. (Exception from
HRESULT: 0x80310007)
At line:1 char:1
+ Resume-BitLocker -MountPoint “F”
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Write-Error], COMException
+ FullyQualifiedErrorId : System.Runtime.InteropServices.COMException,Resume-BitLocker”
In original computer it wouldn’t detect hard drive, so i moved to another machine. Do i Need original computer where drive was installed to have it unlocked?
#2 by Bob Mitchell on August 20, 2018 - 3:02 PM
Try the steps outlined in this article.
https://www.msdigest.net/2016/05/how-to-repopulate-tpm-with-bitlocker-recovery-key-after-a-motherboard-replacement/
The BitLocker key is stored on the chip on the computer you removed the drive from. You need to get the key back onto your current system.