In some cases the yellow explamation mark can be “stuck” for a drive. There are some possibilities here:

• low disc space;
• Bitlocker

The most reccomended way to remove the exclamation mark is to turn Bitlocker protection on and off.

In the case you don’t want the Bitlocker, you can turn it off for a drive using command line, as described here.

Run the command prompt as adminstrator and enter the command:

manage-bde C: -off

You can check the drive status with

manage-bde -status

You will get something like this in response:

BitLocker Drive Encryption: Configuration Tool version 10.0.19041
Copyright (C) 2013 Microsoft Corporation. All rights reserved.
Disk volumes that can be protected with
BitLocker Drive Encryption:
Volume C: [Sys]
[OS Volume]
Size:                 953,24 GB
BitLocker Version:    2.0
Conversion Status:    Decryption in Progress
Percentage Encrypted: 25,1%
Encryption Method:    XTS-AES 128
Protection Status:    Protection Off
Lock Status:          Unlocked
Identification Field: Unknown
Key Protectors:
    External Key
    Numerical Password