I finally got back to this. While investigating in Device Manager I noticed that after a reboot the Sonoff Dongle listed under Other Devices said it did not have a driver installed! This surprised me a bit as I thought it would have been the same CP210X driver that the previous dongle used but anyhow I installed the CP210x USB to UART Bridge Virtual COM Port (VCP) driver and now the Sonoff showed up under Ports as COM 5. I then went into Virtual Box settings for Home Assistant, selected USB, clicked on the +icon and found a new entry called Cygnal Integrated Products Inc. CP210x UART Bridge. I ticked the box and rebooted and all is well. From a restart or full shutdown and startup the system now completes the startup with the Sonoff dongle recognized and operational in Home Assistant.