Question 1

Install fails or rolls back?

Accepted Answer

disconnect the SLP 620, close label software, run the manufacturer’s 620 driver installer as administrator, and remove older SLP software before retrying.

Question 2

Device not detected?

Accepted Answer

confirm the printer is powered on and use a known-good USB cable/port directly on the PC. In Device Manager, remove any unknown/error entry for the SLP 620, then reconnect and install the driver.

Question 3

Version conflicts or duplicate printers?

Accepted Answer

uninstall old SLP drivers and duplicate 620 queues in Settings > Printers & scanners and Device Manager, restart Windows, then install the correct 32/64-bit driver for your Windows version.

Smart Label Printer 620 Driver