Workplace will check to see if you have a local drive that is encrypted, as per your applicable security policy. If someone gains physical access to your computer and your drives are unencrypted, that person could extract the files from the drive. Encrypting the data is a highly effective method of preventing data extraction. If Workplace indicates that one or more local drives are not encrypted, you'll need to encrypt them. The encryption process can take hours to complete, it is a best practice that you do this at your earliest convenience outside of business hours.
Recent Pro, Enterprise, or Ultimate editions of Windows offer a full-disk encryption feature called Bitlocker, built right into Windows. To turn this on, sign in with an administrator account, open the Control Panel and search for "manage BitLocker." This will bring you to where you can select a setting to "turn on Bitlocker." There are also quite a few third party solutions if you can not use native encryption tools.
On a Mac, you can open System Preferences and search for "FileVault." This will open the Security and Privacy Pane. Click the lock icon in the bottom left and enter your Administrator username and password. You can then select the option to Turn on FileVault.
Remember, you do need to encrypt all of your local drives and it is expected behavior that this process could take up to a few hours.
If for some reason you cannot currently encrypt your device to satisfy the device security check, you may be able to contact your local admin or IT support to grant you a one-time exception so you can continue on.
Once your you've got all of your local disks encrypted, refresh the Workplace security checks page or go back to log into your portal. Once resolved, Workplace will indicate that you have passed the check and you can proceed!