Sometimes when you mount a container as a disk with a drive letter, the operation starts, the disk is mounted,  but later Windows encounters a problem with the letter

and does not show the disk or does not assign the chosen drive letter.

The following  trick with Disk Management usually helps to restore the corresponding entry in Windows Registry and to manage the problem:

- Go to Disk Management: click 'win+R', type 'diskmgmt.msc'.

- Find the mounted BestCrypt virtual disk in the list (you can recognize it by size).

- Right-click on the  BestCrypt disk and run  "Change drive letter and Path" command and set the desired drive letter for the BestCrypt disk.