If you are using any of the following programming adaptors:

  • uUSB-PA5-II
  • gen4-PA
  • 4D-UPA

This is caused by an issue with the Windows 10 driver of the USB-to-UART chip. This can easily be solved by using the Windows 7/8/8.1 driver that you can find here.

If you are using older 4D programming adaptors, this forum thread might help.