Please note that formatting the OPTAC Download Tool will wipe all contents of the device.
Switch on the device, connect it to the PC and open File Explorer. Go to "This PC" where the device should appear as 'OPTAC_TOOL'.
Right click on OPTAC_TOOL and left click on 'Format'. Wait until the 'Format'-window opens.
Leave the default options, however please note that the Capacity should be shown as 15.5MB. If not, do not continue.
Click on 'Start' to proceed with the formatting.
Wait for the formatting to complete then unplug the USB cable from the OPTAC Tool. Switch off the device, wait 5 seconds and then switch it on again.
The OPTAC Tool should have a green light above the power button and is ready to use for downloading again.