Before you can use the Flash Online option from the recovery menu on the PULSe 4K Mini you will need to flash the OpenBh 5.0.x_recovery_emmc.zip
To do this download the OpenBh recovery file from the downloads section and then extract the zip file to the root of your usb stick.
Then power off your PULSe 4K Mini, and insert the usb, then press and hold the reset button on the rear panel, and keep holding it when you power on the box again.
You will see the Red light on the front panel, power on, and then flash (you can release the reset button once the red light starts to flash).
When it stops flashing, the recovery flash is complete and your box will reboot.
You can then boot into the recovery and use the Online Flash option.
To do this download the OpenBh recovery file from the downloads section and then extract the zip file to the root of your usb stick.
Then power off your PULSe 4K Mini, and insert the usb, then press and hold the reset button on the rear panel, and keep holding it when you power on the box again.
You will see the Red light on the front panel, power on, and then flash (you can release the reset button once the red light starts to flash).
When it stops flashing, the recovery flash is complete and your box will reboot.
You can then boot into the recovery and use the Online Flash option.