Firstly, reboot your computer, log in using your Administrator account and try accessing the (D:) drive. If you can't, remove Secure Folder (Control Panel > Uninstall a program) and try again. If it still doesn't work, right-click the Computer icon, select Manage and open Disk Management utility. Right-click the (D:) drive below the Volume list and select Change Drive Letters and Paths option. Click the D character, press the Change option and select another letter from the Assign the following drive letter drop-down list. If it still doesn't work, use
firstname.lastname@example.org email address to get in touch with the developer.