Sometimes, Windows can end up thinking a removeable drive should not have a drive letter.
If this is happening to you, you can fix it by:
To assign a letter manually or change the letter you need to perform the following steps.
Open Computer Management by Win + X > Computer Management.
Expand Storage and click Disk Management.
Right-click on the disk with no letter, and select Change Drive Letters and Paths.
Click Add, select Assign the following drive letter and select a letter of your choice.
Finally, click OK.
If the Kobo does not appear as a device in Drive management, then you have a different problem and can ignore this post.
More Details and more involved troubleshooting steps can be found here:
https://www.thewindowsclub.com/windo...atically-fixed