Many PP-6900 units are still running on legacy POS systems (Windows Embedded POSReady 7 or XP). Posiflex has legacy driver archives for these systems, but note that with Windows 7 due to changes in the USB printing stack. If you are migrating an old PP-6900 to a new Windows 11 PC, you must download the specific "PP-6900 Win10_11 64bit" driver package.
Here’s a helpful, real-world story about finding — a common headache for retail and hospitality IT folks. posiflex pp 6900 drivers