UUID of the medium does not match the value stored in the media registry
If you try to load a VM to VBox and it name previously exists in the records with a different UUID, you will get this error.
In VBox you will see a message that said your hard disk is inaccessible.
To fix it, you need replace the new UUID in the configuration (.vbox file) of your VM.
Copy from ~/.config/VirtualBox/VirtualBox.xml the respective UUID from your virtual disk (see MachineEntry uuid).
After, replace the UUID in your .vbox configuration file inside your VM folder.