If you have a more specific scenario or additional details about where you've encountered the term "Key ID," I could offer more targeted advice.

Sometimes, when you plug your Brother PS300B into a Windows 10 or Windows 11 PC via a USB-B cable, the system will ask for a “Key ID” during the driver installation. This is actually a generic Windows prompt asking for the .

: Some versions of the installer require the original PS-300B CD-ROM to be physically present in the disk drive during the verification process.