I found a solution.
First don’t panic, the files aren’t gone. But the USB is locked and you have to unlock it.
Here is what I did.
In the address bar of the browser enter http://volumio.local/dev/
Under SSH click Enable
open command prompt on PC
enter ssh volumio@ip address of volumio device (ex 192.168.1.2)
after successful login type cd mtn … enter
dir … enter ~ displays a list of mount points
cd USB … enter ~ note all caps at USB
dir … enter ~ displays name of mounted USB devices the device should be there
type umount /mnt/USB/name of device (ex MUSAAC) ~ note caps at USB and your device name …enter
plug in USB drive (with everything you hold dear)
go to volumio.local
settings
sources
click update or rescan, don’t remember which it was
volumio should identify media and start to scan, files appear
after scan completes go to music library, USB is present again and the files are all back like it never happened.
go back to volumio.local/dev and disable SSH ~security
used this link to find solution, last comment. Unable to add/modify/remove mounts using webui - #16 by Richardtrimble
Linux will make it seem like the USB is broken and everything is lost. You plug the USB into another device and it doesn’t do anything. You plug the USB into Volumio and nothing appears. You’re like fek! Volumio ruined my SSD wtf? The USB just needs to be told to allow access again. When you plug the USB into RPi Volumio thinks the USB is plugged in but the connection has been cut and needs to be reset all the meta data regarding your precious files is gone and so it appears to be blank. Not so. I hope this helps.