The DPM and other dictation devices incl. mass storage devices can only be displayed and used once in the system after a system restart.
Do you use Bitdefender?
There is a problem with Bitdefender versions <*-56. Bitdefender has released the update *-56. Please update to this version and then restart your system.
If you are using the free version, you can/must uninstall it to be able to use your USB devices (e.g. DPM).
You can now use your DPM on your system as desired.