These are the steps for this issue:
1) Try rebooting both the device and your computer
2) If that does not work, find the files driveinfo.calibre and metadata.calibre on the device
and delete them (you can use Windows Explorer or a file manager on the device itself to do this)
3) Reset the device
If none of those work, you can use one of the wireless communication methods described here:
https://manual.calibre-ebook.com/faq...kindle-fire-hd