Cause
The driver may have been deleted.
In the state in which both GP-Pro EX version 2.22 or earlier and GP-Pro EX version 2.50 or later are installed, if you uninstall GP-Pro EX version 2.22 or earlier, the USB data transfer cable driver will no longer be recognized.
Solution
The solution to this issue is different depending on the GP-Pro EX version.
Cases in which versions 2.22 or earlier and version 2.50 are installed
From the Control Panel [Add or Remove Programs], restore GP-Pro EX version 2.50 (or if only the Transfer Tool is installed, repair the transfer tool), and re-connect the USB data transfer cable.
Cases in which versions 2.22 or earlier and version 2.60 or later are installed
From the Control Panel [Add/Remove Programs], uninstall the [USB Data Transfer Driver] or GP-Pro EX version 2.60 or later. After GP-Pro EX version 2.60 or later is uninstalled, connect the USB data transfer cable.