Certain Drive Not Showing Up

My PC isn't equipped with a floppy drive but.........on the Disk Manager, I have my pendrives set to drive A: and B:

I haven't tried my A: pendrive but my B: pendrive doesn't show up on the drive list. I restarted Recuva and it didn't work. I would appreciate it if B: drive support was added. And I guess A: drive if it isn't in there. ;)